Wha...? - Ehsan Ghaem Maghami VS Mustafokhuja Khusenkhojaev @ World Rapid 2022

https://www.youtube.com/watch?v=lDHMA5e37k0&t=597

And Nakamura vs Harikrishna in the last game, Naka continued desperately until 50 or 75 moves were achieved

i hadn't heard about that one
https://www.youtube.com/watch?v=Ax5U6fOiw9s

at least the arbitor remembered to end it at 75 this time!

Nope, only after 83 moves.  Of course it didn't matter, also not if it was some sort of special treatment for Nakamura.

83!? So they learnt nothing from the chaos that erupted with Maghami VS Khusenkhojaev?!

Well, here there was no possible ambiguity - with rook and knight vs. rook black was in no danger of losing. Maybe the arbiter wanted to be absolutely sure (and moves were blitzed out which could explain some delay between being totally sure and stopping the clock). Or he wanted to give Nakamura a chance to quit himself - but Nakamura had just declined a "draw offer" (opportunity to exchange rooks).

At the end of the video you can see three people in suits, probably all arbiters. The one with red tie who stopped the clock probably had gotten a signal from the one with blue tie holding a scoresheet keeping track of how many moves had elapsed (here no laptops with the live transmission).

Rook and bishop vs. rook is much trickier: the stronger side cannot win against best defense (unless the position happens to be winning from the very start), but the weaker side can easily lose "without best defense". And this can happen at any moment: Here, the black resignation was justified according to the position but he was then saved by the 75 move rule. Actually, white was winning twice before according to tablebases - "live engines" don't show it because the win would have taken beyond move 50.

There was another case where the weaker side was losing and resigning after 51 moves. But he could have tried one "defense":  claim a draw according to the 50 move rule. Note that arbiters have to interfere after 75 moves (and can also do so in retrospect), but a claim according to the 50 move rule has to be done by the player. In our case, the arbiters had to refute the claim based on a threefold repetition (the black rook had been on different squares),  they couldn't help the player - even if they wanted to - by applying the 50 move rule or giving him a hint.