The regulations say
The permanent starter is a steward who oversees the start procedures, Charlie Whiting used to do it as race director but since his passing it became a separate role.44.10 When the cars come back to the grid at the end of the formation lap or laps, they must stop within their respective starting grid positions, keeping their engines running.
a) There will be a standing start, the signal being given by means of lights activated by the permanent starter.
b) Once all the cars have come to a halt the five (5) second light will appear followed by the four, three, two and one second lights. At any time after the one-second light appears, the race will be started by extinguishing all red lights.
Now to the footage:
https://i.imgur.com/uwVGHbu.mp4
When the marshall with the green flag starts going there's still two cars out of position on the right, it looks like Piastri stopped one row too early, Gasly behind has to wait, Piastri moves up and when the camera changes the Alpine is still moving and maybe comes to a halt a tenth of a second before the first light goes red.
The other thing is the light boards on the pit wall, they tell the drivers where to go and once they are in their grid slot the driver side turns off and the other side goes green, showing the permanent starter that the car is in position.
Looking carefully it's clear that the green light for Gasly isn't on until there's already 2 out of the 5 red lights
Judging by his start it did not seem to have impacted Gasly in any way, meaning he managed to do all the necessary pre-start procedures on the wheel but sticking to the regulations strictly the race start procedure was initiated prematurely and the race start probably should have been aborted?
I personally don't remember seeing anything like this.