As best as I can tell this must have recently changed as all sorts of stuff started acting strangely and I see a bunch of other people reporting similar odd issues.
The bogons alias includes, in addition to bogons, !10.0.0.0/8, !172.16.0.0/12, !192.16.0.0/16, etc. This is fine if you're using it alone in a rule to block as-intended, but if you've e.g. added it into an additional alias with private networks and are blocking on that...suddenly things can go haywire. E.g. a rule that *was* blocking "bogons and private IPs would now potentially be blocking bogons and NONPRIVATE IPs which is...unexpected.