Confirmed ... it is Signature Bank that made the change.

“One of our fiat banking partners, Signature Bank, has advised that it will no longer support any of its crypto exchange customers with buying and selling amounts of less than 100,000 USD as of February 1, 2023. This is the case for all of their crypto exchange clients.

No other banking partners are impacted, a Binance spokesperson said.

So Binance isn't the only exchange that uses Signature Bank. Expect announcements from other exchanges soon.

But Binance has relatively very few customers that are using Signature Bank:

Binance said it’s “actively working to find an alternative solution,” in the statement. And that “0.01% of our average monthly users are serviced by Signature Bank.”

Binance Says Signature Sets Transaction Minimum Amid Pullback
https://www.bloomberg.com/news/articles/2023-01-22/binance-says-signature-sets-transaction-minimum-amid-pullback [Archive]

If I could edit the title of this post I would, to indicate this affects "some" customers.