The only thing that comes to mind here is that there was a fee spike [1] and they've got too many unspents stuck in the mempool and can't initiate further withdrawals because their wallet is effectively "spent" until those pending transactions complete and they receive their change. I find this a bit hard to believe though...wallet management isn't simple when it comes to the scale that Binance handles, however I'd be shocked if they didn't have code written to trigger CPFP (Child Pays For Parent) [2].

[1] https://jochen-hoenicke.de/queue/#BTC,30d,weight

[2] https://bitcoinops.org/en/topics/cpfp/