MacRumors reports Restoring a Bricked iMac Pro Requires a Second Mac and Configurator 2:
"If an iMac Pro becomes unresponsive and requires restoring, like if there's a power failure during a software update, there are a special set of instructions iMac Pro users must follow, which require a secondary Mac."
As outlined in an Apple Configurator 2 support page, an iMac Pro restore requires a second Mac running macOS High Sierra with internet access and Apple Configurator 2.6 or later installed.
[...] This restore process is similar to what must be done for an iPhone or iPad that is unresponsive, and it is necessary due to the extra security afforded by the Apple-designed T2 chip ... [which] integrates the system management controller, image signal processor for the camera, audio controller, SSD controller, a Secure Enclave, and a hardware encryption engine.
(Score: 2) by RedBear on Monday December 18 2017, @02:44PM
Or bacon... glazed with maple syrup.
My presumption is that if you're the kind of person who doesn't like the idea of secure boot you will have disabled those security features already and therefore should never encounter the recovery problem. And since it's easily disable-able it's not a good reason to avoid buying a Mac if you already like Macs.
¯\_ʕ◔.◔ʔ_/¯ LOL. I dunno. I'm just a bear.
... Peace out. Got bear stuff to do. 彡ʕ⌐■.■ʔ