@MrIncognito
Those are compelling reasons as to why this feature should stay rejected yeah. The only one I thought of before reading your post was the 'speedscan' one.
But to play devil's advocate, if this feature were to be optional, the speedscanners would only benefit from the small portion of users that actually turned this option on (assuming it's turned off by default, which it should be ofc) to begin with. By this, I mean that the users with this feature on most likely wouldn't care too much about translation quality, as long as the translation is acceptable enough to be on the site. As for the users with this option off (the majority), they would be more likely to wait for higher quality scans/translations, as they already do. The silencing of (usually) better translations would only occur for the small portion of users that turned on the option in the first place.
Then again, it would stand to reason that most users that read the option and its description wouldn't understand its implications, and possibly stunt their reading experience by turning it on after thinking "oh yeah that looks helpful".
But yeah, I was never in favor of this suggestion to begin with lol. Like you and comeonnow already said, this isn't a usual occurrence, which pretty much makes it a non-issue.