IIRC (having trouble finding my source), MAS*H was shot on film but in 4:3 AR. It's been released in HD/Blu-ray now by being re-digitized but each scene has been cropped to be 16:9.

There's going to be a dead spot of TV/Movies where things were shot in SD on Video where they will be forever SD but older things, shot on film, can be brought to HD and newer things are either shot on Film or HD video.

I'm curious to see how quickly the things shot in HD Video become outdated by superior resolutions of 4k, 8k and whatever comes after and if there's a plateau of consumer/home resolution.