Why in God's name would you want Brussels telling you how to plug your computer in?
Firstly: you're begging the question here. Is it bad for Brussels to say this?
Secondly, Brussels ain't telling me shit, because I'm not in the EU. Brexit, fuck yeah etc. I do nonetheless reap the benefits of what Brussels are saying here.
Thirdly, Brussels aren't telling me how to plug my computer in. Even if I were in the EU, I could basically do what I want. I could open it up and attach a barrel jack. I could cut the cable and splice in a 48V supply. I can even buy a dodgy shit USB-C to barrel jack and power my ancient laptop from any of the many supplies I have. I can do any of those things and no one is telling me I can't.
What Brussels IS doing is telling manufacturers that they have to make devices that accept and emit power according to a particular set of standards. I'm guessing your government already does this with AC powered devices, specifying voltages, frequency, current, plug mechanical design, thermals, tolerances on those and of course a whole other bunch of shit, so people can buy a device from any vendor and safely plug it into power from any supplier in any part of the country.
What makes you think they have any idea what the right answer is,
1. What makes you think they don't? Face it, you don't have a better idea.
2. We know they do because the charging standardised on USB-C is infinitely better than the utter mess of proprietary shite we had to deal with before.
or that their answer will continue to be right for as long as the rule is in place?
Well USB-C has so far held up for 11 years and is only becoming more common, so I don't think it's going away any time soon. But if it is... gosh if only the law was written in such a way that the specifics are subject to review from time to time...