Lol
. They are funny little things. They pile substrate round the house when they feel the cold in my experience. Ours start doing it in about August when the nights her cooler and keep doing it right through to summer. They also like to block k up the entrance door so it’s darker inside. They do need somewhere to retreat to that’s dark (especially as they sleep during daylight!). The tipi - he either doesn’t like it but does like it snd isn’t sure what to do with it so playing with it like a toy. A bit of a game. He tips it up, you straighten it - he tips it up again.
I think it’s perfectly normal behaviour. In terms of cleaning out - a litter tray really really helps. Syrian hamsters will use one if you put it in their chosen pee place - often a corner of the cage. A corner tray with sand in and they will pee in it. You then just empty the litter tray and the house should stay clean and dry inside. Baby hamsters still havd the odd accident where they pee in their nest but tend to grow out of it.
If you clean out too much and disturb his house and nest too much, he will work even harder to bury it as they don’t like their house and nest being disturbed. They are very precious about the nest and their hoards snd if hoards are removed they can start peeing on them - to deter people from stealing them and mark them as their own. Then it’s a bit of a vicious circle. Although the cycle can be broken eventually.
After going through all this a few times I now give them a large house- large enough to fit a litter tray inside and with a roof that lifts off. Easy to empty the litter tray. If they have a large house that’s dark inside they are more settled and have normal habits of nesting , hoarding and peeing in there, in separate areas. Putting a bendy stick bridge/tunnel over the entrance door helps make it dark inside (light can’t go round corners either so the ends of the house will be dark - away from the entrance). You could do that now with your current house.
It looks like you have space for a larger house though. If a house is too small they won’t use it (the tipi may be too small). Syrians generally need rat sized houses, tunnels and hides etc. Most things sold for hamsters are only big enough for dwarf hamsters. A few more floor toys like large tunnels may help him feel more secure and they also like overhead cover - something to sit under like a shelf or roof hanging rat Sputnik.
It’s also normal for them to forage at night and keep busy organising their home. They are very active at night. I often find in the morning that there’s a big hole in the substrate down to the cage base and a big pile of substrate next to the house (insulation and also makes it more like an underground burrow). So I just add more substrate to fill the hole!
A shoebox house is a good size and cheap - you just cut the base out of the box snd keep the lid for a lift off roof and cut a hole for a door - plus bendy bridge tunnel entrance.
Or a guinea pig house is a good size (whether you put the litter tray inside or elsewhere). Labyrinth houses with well too as they are automatically dark inside - if they’re big enough - but they can be expensive. He may be happy with the current house with a bendy bridge over the door.
They like extra hidey places too - coconut hides are popular (round). Our previous Syrian used to sit in his every evening for a wash after waking up.
If you’re cleaning out a lot, it isn’t necessary and can stress them as it removes all their familiar smells (and doesn’t help with bonding/taming if they see you as the disruptor!). It’s only their pee that is smelly and unhygienic. So spot cleaning the pee area is all that’s necessary once or twice a week (eg taking the odd handful out snd replacing it). With a litter tray you just empty that once or twice a week and the rest of the cage should stay clean and dry. Poops aren’t really dirty or smelly and can just be spot cleaned if there are quite a few - picked out. Sometimes they hoard some of these too as emergency food supplies (they sometimes eat their poops which is normal behaviour - they have two stomachs).
Have you thought about trying paper bedding like Fitch? I switched to that from shavings years ago. Hansters love it as it’s soft - less messy when piled up as it holds its shape better. It’s also dust free. I started by mixing Fitch in with the shavings snd then switched over to it completely.
With a litter tray and spot cleaning you can easily go three or four months without changing the substrate - so saves on substrate as well as smells
Main thing is to not clean everything at the same time as it removes all their familiar smells. So if you do the substrate , don’t clean anything else at the same time and keep back some of the old clean substrate to spread on top of the new so it still smells familiar- that layer will get spot cleaned out eventually. Then wheel another week, any toys another week again etc.
Too much cleaning out may also maje him want to hide away more from you. Sorry if you already know all that akready.