Please don't take this the wrong way, but were you trained in the arcane arts of typewriting? The only time I've seen anyone do double spaces after a punctuation was when dad taught me how to use the typewriter as a kid.
Yes, I was trained on a typewriter. My fingers insist on the double space and my brain is no longer involved in the process. I don't think I could change now, no matter how much I wanted to!
To give you an idea of the timeframe, I came first place in my typing class, an achievement for which I was awarded a Brashes voucher 🤣
Ha, nice catch! I recently noticed an older colleague doing the double spaces and it brought back memories of my mum teaching me how to type. Not sure when I dropped it, it looks weird to me now once I notice it.