Even in this poorly made comparison shot I made you can tell the difference between streaming and "self hosting"
(lemmy.world)
Jack Ryan S3 E3
Yeah I really doubt streaming would change anything to 4:3.
Disney+ famously changed classic Simpsons to 16:9 and in the process, cropped enough to make some visual gags not work, but I can't imagine them preferring 4:3 over 16:9.