Deleting messages in the Mail Archive folder causes deletions in other mail folders
Recently I decided to thin out my mail storage usage at Google as I was reaching a limit. I use organized mail folders extensively for saving messages I care about and allow my Inbox to grow with the rest - periodically deleting excess from Inbox from the bottom every year or so. However, I began to notice the Archive which I never used nor cared about growing larger and larger. I was never even aware of this Archive in the past and I've been using Mail for many years. Now, I needed to include it in searches when looking for recent emails I needed to find (ones not filed away). When it came time to reduce my mail storage I figured I would thin out the Archive "folder" from its huge list of old mail up to the year 2020.
A month later, I've noticed that my valuable mail saved carefully in folders has also been thinned back to year 2020.
It sounds crazy to me but - is this Archive folder not actually a folder at all, and does it actually point into my own folders? Did I really delete all my precious mail stored away deliberately and intentionally by some dangerous new behaviour added to Mail? Its gone on Google's server as well. Yikes! Can I get it back?
MacBook Air 13″, macOS 10.15