Because the hinge is behind the BB and they use a common RD, you will have the greasy chain going slack,
and coming off the chainring(s) when you use the rear fold.
eye the Type extension loop Birdy uses as a potential way to gather up some of the slack ..
Because the next step , packing in a suitcase when actually traveling , the greasy loop of chain can be bagged, in practice..
to be a little bit less Messy..
but once in hand you can practice to get your own scheme sorted out..