That’s interesting, C. Horror.
In general, my experience matches up with what you’ve posted and I have no reason to doubt you.
I tried to replicate it by finding a thread that was inactive for over a year. The topics suggested were ones that I was active in recently, so perhaps this is some manner of edge case. I dimly recall the thread I was reading (before being given a suggestion) was an older thread with recent activity, and I recall the thread I chose to read and almost-necromanced was one about SEO optimizations (Companies that sell SEO services)
I know that’s not really useful data. If I can replicate it again, I’ll try to recall to take screenshots and note what I was doing.