> That's been said for years, and hasn't held true.
It certainly has. Unsigned binaries were recently deprecated entirely on M1 Macs. Microsoft even released versions of the Surface that can only run Windows and only run apps blessed by Microsoft. With each iteration on these products, the screws are tightened a bit more.
Software freedom is not just about being able to run Linux. Most Mac users buy Macs because of macOS and its integrations, running Linux doesn't help them out. Software freedom on macOS definitely does, though. As it stands, that freedom has been chipped away at with new releases of Apple's software and hardware.
For example, I'm the author of several open source utilities for macOS. Users had no problem using the utilities a few years ago, but because they're unsigned or not Notarized, macOS tricks users into thinking that they're either broken or malicious. Even self-signing the apps has macOS treating them as if they're radioactive. Users don't understand the scary signing and certificate alerts, so they end up thinking they've downloaded malware. The solution to this is to pay Apple $100 every year, and then regularly have them scan and approve of the apps via Notarization. That's antithetical to software freedom. Regular users who want to use un-Notarized software are left frightened and without having their needs met. Software freedom is important for everyone, not just developers and power users.