That is a PON panel (Plug-On-Neutral). Siemens is one of the only that are now making a AFCI that doesn't require the neutral to land on the breaker allowing it to be used on MWBC. Most others will trip from load difference between A & B.
If the Siemens AFCI doesn't require the neutral to land on the breaker, and, it's not prone to tripping because of a load difference between A&B, what's wrong with this install?
Jap.