In case it was not immediately obvious, this discussion is not about the Surface RT, but about the Windows Dev Kit 2023. It ships with a different Windows version, on a different Arm architecture, with different policies regarding locking down.
And? "In case it was not immediately obvious" by me specifically pointing an MS ARM device, MS's "policies" when shipping ARM devices have been much more locked down than x86. Around 50% of ARM devices released by MS so far have been completely locked down, incapable of running anything except for some version of Windows. Not just "FUD by nerd circles".
All ARM64 Windows devices have been "bootloader-unlocked". That has been the case for the last 5 years. Windows RT and Windows Phone devices are literally irrelevant to this discussion regardless of your anecdote.
In the past 5 years, how many ARM devices has MS released, other than the Surface Pro X ?
My "anecdote" is actually the majority of MS's history so far. You just can't claim it's scaremongering when they have released so many locked down ARM devices it's hard to remember all of them, and definitely easier to just remember the few "unlocked" devices they have ever released (just the X?).
And also "obviously" we should mention that even in the so-called unlocked Surfaces you are still forced to entirely disable Secure Boot in order to run Linux or _anything else_, with the consequences that implies. For example, it is dubious you will be able to load future versions of Windows, since those will require SB to be on (W11 already officially does, even if it doesn't seem to enforce it -- yet). A properly unlocked device would allow you to load your own signatures while keeping SB enabled.