[trasz2]

Also most Linux machines, like phones, also contain instances of things like SEL4, often a couple of them.

And Linux... well, it managed to accumulate a lot of historical baggage for something that young. Device numbers are another example.

[TristanBall]

Nearly 30 years seems like plenty of time?

Many projects manage to accumulate plenty of tech debt in 30 months, without being a deliberate work-alike reimplementation of an existing system.. which I suspect means you're already starting with a certain amount of baggage.