app bundles (which I still think are just fantastic) were a NeXT thing.
App bundles were just a better implementation of resource forks, which were invented by Apple and pre-dated NeXT.
(which of course became Apple, but they weren’t at the time)
NeXT was founded by people who worked at Apple (not just Steve) and they were largely put in charge when they came back to Apple. I wouldn’t call them separate companies. Just a weird moment in the history of the company. A lot like what just happened at OpenAI.