If a bank classifies their long-duration Treasurys as held-to-maturity, they don’t need to mark the fluctuating value of the bond principal to market. [0]
Also, most other banks aren’t overly concentrated in one area that could collapse and force a bunch of customer withdrawals like Silvergate was (in cryptocurrency)
If there was a problem in banking bond holdings, it likely would’ve surfaced by now with the massive interest rate changes.
[0] https://viewpoint.pwc.com/dt/us/en/pwc/accounting_guides/loa...