BTS could have just directly told exchanges about it a week or 3 before the swap/change/update.
Assuming that exchanges are keeping up with any particular projects development just makes everyones lives harder.
It's not that hard to just mail exchanges some info and offer support (if needed) for the update.
To be honest, update was coordinated with delegates and delegate participation rate drop to 30% right after the snapshot, but even at chain with so small delegate participation rate Bittrex and few other exchanges keep process deposit/withdraw.
Everybody was quite confident that if even some exchanges somehow miss 4 weeks notice, they will stop deposit/withdraw automatically and nothing bad will happened.