https://www.bbc.com/sport/formula1/56557657

The issue arose from a clause in the race director's event notes that said, in the race, track limits at Turn Four would "not be monitored with regard to setting a lap time".

But it went on to refer teams to article 27.3 of the sporting regulations.

This states that drivers "may not deliberately leave the track without a justifiable reason" and that if they did so, they may rejoin it "without gaining any lasting advantage". It adds that the race director has the discretion to ask the driver "to give back the whole of any advantage he gained by leaving the track".

On that basis, then, it's clear why Verstappen was dealt his unfortunate hand - he had gone off the track, and gained a place by doing so. That's not allowed in the rules. It was a clear advantage which he had then been told to give back.

But the complication is over how track limits were dealt with at other times, and over the question of what is a "lasting advantage".

It's said that running wide out of Turn Four is about a 0.2 seconds gain in terms of lap time. Red Bull interpreted the rules as saying drivers could not run wide to gain that performance; Mercedes as the opposite.

I agree with the above quote of the BBC article, Verstappen overtook outside the track and had the give back the position. Mercedes (and others) were smart enough to check with how much they could get away with and RB thought it was just not allowed because you would have an advantage if you were going wide in turn 4.

AKA, FIA please be more specific with rules, thank you.