I found the flag to disable it, but I’m really curious why the decision was made in the first place. On Chrome and Firefox, l If you double click this example HTML5 : https://www.w3schools.com/html/html5_video.asp, it will go full screen. I’ve always wondered why sometimes click on a video would make it go fullscreen, it’s laggy and annoying for me, even on high-end laptops. On My Mac, as well as in Windows and Fedora VMs.
It was probably done to accommodate both mouse and keyboard users and touchscreen users.
Never had an issue with it though.