Devil’s advocate post since I admit they are are a bit of a long shot.
Does it matter how far they are behind? It’s not like we seem to be at a development plateau or anything. Apple can skip some steps by learning how other systems are working or solved issues.
Not to mention each company seems to be doing their own thing instead of uniting. So even if Apple didn’t have that strong vertical integration/monopoly mindset they’d probably have to do this anyway if they ever planned on making a car.