I don't know who started the idea of friging a cake to 'set' the crumb coat but that was *never!* done before.
A crumb coat is a super thin coating of b'cream icing that is allowed to dry at room temp. This should take only a few minutes (not much more than 15 minutes at most) depending on the icing recipe being used.
IF the recipe is a non-crusting one, then yes, friging is probably needed. The thin coating of b'cream should look much like a glazed donut.
It is intended to seal in not only crumbs but moisture so the cake will remain moist while being worked on.
Once you can lightly touch the crumbcoat w/your finger and nothing comes off it is ready to be finished iced.
And once the finished icing coat is done you are ready for the fondant. In fact, the b'cream needs to be fresh for the fondant to adhere to it - not refriged nor allowed to dry/set up.