Unless I'm misunderstanding UEFI, that's not quite right. Contrary to the headline-hype, I believe Microsoft's OTHER explicit requirement for certification is that end users must be furnished with a way to disable it that's impossible to do by mistake, but entirely possible to do voluntarily. For example, flip a DIP switch, place or pull a jumper, enter a 32-character encryption code printed on a tiny sticker permanently affixed to the motherboard, etc.
Installing Linux already has a reputation for being technically challenging (even if it actually isn't, these days, but whatever). What you're saying is that, unless distros jump in on the secure boot ship, then they'll have to add to their installation instructions something like "depending on the make of your motherboard, you'll need to open the computer and perform one of flipping a DIP switch, placing/pulling a jumper, or entering a 32-character code that's written on the motherboard".
That, alone, will desktop kill Linux for non-techies. And if that isn't worthy of anti-trust investigation, I don't know what is.