If you don't know why they want to lock it down, if Apple says they don't want to lock it down, and Apple Silicon Macs show no further evidence of things being locked down (they're just different), then why do you still think it's so evident they will lock it down? I honestly get the impression you're caught up in some narrative that has very little substantiation, just a fear that macOS will become iOS.
> I rather watch their actions.
And which actions are those? Gatekeeper and the Apple T2 are not enough to make the Mac not an "open computing platform", let alone something close to iOS. I'd argue they're not even on the way there, just like Windows SmartScreen isn't on the way there. And note that the T2 is even gone from Apple Silicon Macs.
Apple deserves all the added scrutiny in this area because of their attitude on iOS [1]. But there's absolutely no reason to believe that Apple's direction towards locking down Macs is either "clear" or "inevitable" in my view.
[1]: There are some identifiable explanations as to why iOS is so locked down whereas the Mac isn't, but let's talk about that some other time.