Both WebGL2 and WebGPU are probably the most 'watertight' specced and tested 3D API ever built, and especially WebGPU has gone to great lengths to eliminate UB present in native APIs (even at the cost of usability).
We only need to open chrome://gpu and see how many workarounds are implementated.
Those that happen to own a device where workarounds are yet to be implemented, have quite interesting experiences, depending on the root cause.
As this is an increasing list across Chrome releases.
Lets see how it works out there with Firefox and Safari, the later still not fully WebGL 2.0 compliant.
So much for the watertightness.
What I really would like to see is browser vendors finally providing WebGL and WebGPU debugging tools.
I think a decade has been more than enough for that.
Then again, no one is paying for browsers, so I guess I should not complain.