I wouldn't use Greenies at all,there are just too many cases of them being unsafe and the ingredients are always questionable.They use "fruit" colors or something like that(some sort of unspecified fruit based dye,forget the exact phrasing they use,but unspecified regardless)which could mean anything therefore is honestly not worth risking.
There are way better biscuits than Milk Bones especially in the US(even if there weren't I would still never use them with the exception of a few that have decent ingredients,not hamster safe though),so I'd agree on that
For example Sojos have some hamster safe biscuits(not all diabetes friendly,though there is at least one flavor that is)as well as Wet Noses and quite a few other brands.Sometimes the dog biscuits may be organic or human grade(Sojos is human grade,Wet Noses are organic)but those things aren't extremely important as long as the ingredients are good and they come from a reputable company.There are a few shady companies out there for dog products(Evanger's and Diamond for example,loads of recalls and sketchy practices)but with the good companies you can usually find some nice treats for hamsters!