Fun fact: Edgar Allan Poe invented the term for a side-quel. A pendant. He did "The Domain Of Arnheim" and then "Landor's Cottage (a pendant to 'The Domain Of Arnheim')". I was like "WTF is a pendant? Is it like a sequel?". It's a side-quel. A different guy wanders into a different part of Arnheim, and meets other different characters. So, that means "Rosencrantz & Guildenstern Are Dead" is a pendant to "Hamlet" and "Alien: Romulus" is a pendant to "Alien". So!! Get spreading that around. I want it in popular usage by this time next week.
Do we really want to make this a Thing that Hollywood will latch on to to continue to avoid coming up with new stories?