Oh Geez, I did recently read about needing to wait until July but I don't have the source now so not sure, perhaps you're right.
In any case, it's a similar big problem if you miss the three month enrollment period.
Perhaps you flee back home in April, in that case you'd have to wait to enroll until January of the next year, effective in February rather than July if you're correct. Still very bad.
Of course a way to avoid this timing problem is if you're PLANNING a move rather than making a move based on an emergency.
In that case you can enroll in Part B while living abroad during the SEP and have it ready for when you arrive.