It's not just 64-bit though. There are also some fake-security "notarization" requirements that were notoriously vague and poorly documented for months, as well as some equally vague and unspecific threats that certain non-notarized applications might or might not cease to work on January 2020. I've been developing for Macs since the late 90s and have never seen less clear developer info.

See the discussion here - and notice how confusing and contradicting the opinions about it are: https://news.ycombinator.com/item?id=21179970