[the_af]

Wait, do you mean it's enabled by default but the author can disable it?

If not, I wonder why I can still watch most videos in their original language (even though I'm in a Spanish-speaking country), and I only encountered this once so far.

[extraduder_ire]

It's being gradually rolled out to channels. Will likely hit larger ones earlier, or following some other metric youtube is following.

[kevin_thibedeau]

There is supposed to be a procedure to manually remove each language dub but it was broken (at least as of last year).