Basically everything applicable to the playpen of a human baby is applicable to the playpen of an AI robot baby in this setup, to at least some degree.

Perhaps the least applicable part is that "robot hurting itself" has the liability of some cost to replace the broken robot part, vs the potentially immeasurable cost of a human infant injuring themselves.

If it's not a good idea to put a "glass vessel" in a human crib (strictly from an "I don't want the glass vessel to be damaged" sense) then it's not a good idea to put that in the robot-infant crib either.

Give them something less expensive to repair, like a stack of blocks instead. :P