No surprises here. Just like the lockdown on iPhone screen and part replacements, Macbooks suffer from the same Apple’s anti-repair and anti-consumer bullshit. Battery glued, ssd soldered in and can’t even swap parts with other official parts. 6000$ laptop and you don’t even own it.
I agree we’re long way from it; but, I don’t think the secure signing of components would necessarily equates to “no reason”, though, that’s definitely not a blanket statement. Personally I’m huge proponent for locking down components with secure signing on the portable devices — less likely to experience theft, if thieves cannot get into the device nor salvage for parts (though right now they just skim passcode and reset iCloud account to circumvent it; but this can be fixed with more security around the workflow). However, for fixed devices, it makes less sense.