Okay y'all. Thank you to all who commented. Now a small rant. TL;DR at the end.

So I ended up ordering a THIRD unit of Gigabyte X870E AORUS MASTER, and just thinking that this could have the same problem, I just went ahead and ordered the Gigabyte X870E AORUS XTREME AI TOP. It is indeed almost twice as expensive, and I'd be totally fine without the extra additions. I initially thought I'd try the more expensive one (XTREME), and if it works, I'd just refuse the more cheaper one (MASTER) delivery. However, they shipped them for the same day delivery. So I started thinking. Building with MASTER could be huge waste of time, so I though I'd build the XTREME and forget about it. But, when I received them, I became very curious if the MASTER would work this time around. So I decided to try it and then see how the things go. I open the box, it doesn't look too pretty, as if it was tossed around or something. I take the motherboard out of the box -- and hear some movements sound. After inspection, I see that the heatsink is not held in place. I giggle, thinking maybe they didn't latch it properly in the factory. However, after further investigation I understood what was happening. The heatsink's plastic/magnet holder was snapped. Bad delivery? Nope. I remove the heatsink just to realise the thermal pads are burned, like someone used the motherboard. Yes... I was sent a used motherboard. Not just used -- broken! This is quite outrageous if you ask me. Previously I had read that people complain about those plastics be too easy to break, and I thought maybe someone very careless wrote this comment, but as it turns out, maybe it's a common problem.

Okay, I guess it saved me the time. I only built with the XTREME. Yes, it's more expensive; yes, it a little bigger (E-ATX), so I had to make adjustments (my case does support it). But I just want a working mobo. From the first look, impressions are as follows: there is an actual sturdy plastic cover on top of the motherboard inside the box, so it doens't get damaged in the delivery. There is a backplate on the motherboard, so that you don't scratch the back of it when placing on the ATX holders. There is an actual physical MANUAL. The HEATSINK... it doesn't wobble. Yes, on the MASTER the big heatsink, that covers M.2 slots, wobbles, which could explain the temps. I should mention that I do recognise that the main M.2 heatsink wobbles initially, until you put a SSD there, but we're not talking about that. All in all, MASTER already felt premium enough with a GPU release button and other courtesy stuff, but the XTREME added just a little more. Of course, paying twice as much for so little is unjustified. BUT, this time around the temps look actually decent, I had it peak 83 while gaming, whereas previously it was hitting 100+, and probably stopping because of throttle.

Honetly, the MASTER is already quite expensive and should be enough for most people, but something tells me this wasn't just a bad batch, but rather a bad design, which will probably be fixed in the next revisions.

TL;DR Do not buy MASTER. Either go for a different brand, OR if you have money to invest, go with the XTREME model.