What's the point of complaining about use of jargonisms in a specialist-leaning spaces?
Anyone with a resemblance of a functioning brain (that is, any "normie" included) can understand "ability to install and run custom aftermarket operating system, or modify pre-installed one", assuming they know what an "operating system" is. And if they don't know what it is, that can - and should (!) - be explained too.
This ability matters to people who don't know any much about any computer programming, because it affects their ability to use the devices they own. They may not know how it all works, but they do express regrets when something doesn't work the way they expect or want it to work. And we all know and hate enshittification here, don't we? Personally, I'm tired of saying "no, because Apple/Google decided only they can control this, and neither you or me can change this on this device" to "can this work so-and-so" questions.
And "open bootloader" is a jargon shorthand for that. Crude, because it should be actually more like "bootloader that can be configured to validate software integrity with user-provided key material", but most people familiar with the space and lingo get the right idea anyway, and shorthand needs to be short. And this is Hacker News, not a Wendy's, so jargon is more than expected.
If someone (a "normie") reads something and don't understand it, we should all be encouraging them to ask questions and try to give them accessible answers. Not shield them from this knowledge, not fetishize mindless consumerism, not behave like snobs, and especially not dismiss something important only because it's not commonly understood.
For marketing materials that target "normie" audiences, it should be just phrased in "normie"-accessible way (look how Valve does that with their hardware), but when we're compiling a HN wishlist from HN comments, complaining about jargon is silly.
/rant