I guess…I don't see anything else really on the upgrade guide that deals with potentially outage-causing issues like this, and they have whole sections on HA considerations.
You could also say, most people doing HA already have lagg groups configured. And while that is also true, it also doesn't excuse the omission of this critical piece of data.
Thanks for the followups and suggestions though, I don't mean to sound ungrateful, this is just a bit too sloppy for what I've come to expect from the pfsense team.