So this delay in withdrawals would prevent a bank run right? 
My thinking: if there are too many withdrawals and Binance had fractional reserves at some point they'd have to pause withdrawals, which would result in widespread panic

I think its to discourage withdraws rather than to delay a selloff

nerd2ninja

[Edit: Oh, .. I see ... to cause a delay of a selloff.]

If I send a deposit transaction to an exchange and the fee wasn't high enough, and I didn't have RBF set, and I don't know about CPFP (or can't use it because it came from a custodial wallet), then my deposit transaction doesn't confirm and I won't be able to sell.

cryptocoin

bitcoin

Binance clogging the mempool?

039957a0bd

Last time Binance did this was June crash. Maybe they know something big is about to hit.