What's the context here? When, where and for what did they recommend SVB?

(FWIW, it did end well, as going with a relatively large federally insured bank meant that no one lost any money during the crash)

SVB was considered the "standard" bank for all startups for decades so it's not surprising that YC would give the same advice. If you run a startup out of a normal bank sometimes you get weird glitches: https://mitchellh.com/writing/my-startup-banking-story

Of course today startups are probably using Mercury/Ramp/whatever.