I Figured it out!!! For the short answer, scroll to the bottom. For the brave of heart...
I had 3 batches that tasted / smelled like green olives to varying degrees.
I ruled out the yeast. (I used the same yeast harvested from previous batches and did NOT get the taste or smell in a subsequent batch. It was Dennys Favorite FWIW)
I realized that I used the same hops in all of them (I have a big bag of hops. Perhaps they've gone a bit stale/old) Before you throw me under the bus for using stale hops... I'm only using them for bittering hops and in very small portions. (here they are fwiw
https://ychhops.com/varieties/herkules)
Batch1; Scotch ale - just a hint of green olive smell/taste in some bottles. Very faint. Only a few could distinguish the smell.
Batch2; Deception Stout - BRUTAL! Pretty much drainpour.
Batch3; Deception Stout - Got a bottle or 2 that were kind of bad. But other bottles are perfectly fine. ??? That's weird
Then I finally put it all together.
I brew in an apartment. I have a pantry that I use to store my beer on the shelves. I also will occasionally put a carboy in there to finish conditioning.
Totally didn't think about the fact that the lightbulb was a compact flourescent because it's a pantry... the light is only on for like... a second... unless you forget it on for days at a time
Batch 2 was left in the pantry for 2 weeks with that light being on for long stretches.
Batch 3 was not - HOWEVER - the bottles that were on the front part of the shelf were light-struck, whereas the bottles in boxes or near the back were unaffected. Hence, some bottles were affected, and others were not.
I've switched to a conventional bulb and make sure to always turn it off. I also don't let my carboys in there anymore.
Conclusion;
It was likely a combination of old hops being lightstruck.