If the units cycle, F-N-R-N-F-N-R , why would it not be able to be started F-N-R and R-N-F (?), using both E units ?
What if one misses a step and gets out of sync? There's nothing to synchronize them. This is the same issue that people double-heading conventional equipment with the electronic reverse boards, and even command stuff that's not lashed up into a single train.
It's easy for them to get out of sync, you do a reverse when one happens to stop on a dead spot on the track, poof you're out of sync.