Yeah we have implemented go-away on https://old.reddthat.com/ but only as a test and it's worked well. I haven't made the time to implement it for our main endpoint.
I also want to do exactly that, only show the challenge for non-logged in users which adds a small bit of complexity but my $job has been flat out recently. So I've only been doing moderation duties rather than server admin duties.
But I can think of plenty of edge cases that something could happen or affect regular users and I don't want that to happen. Normally the bots are all like the ones we just had, using open proxies/residential proxies and querying either posts or the API directly.
I'm hoping to carve out some time in the next month to coincide with this maintenance or our server migration to do some solid testing.