I think that just the absence in official app and the existence of this tool makes this point largely irrelevant. Company in question could easily reverse this decision overnight as the data exist, but absent that people adjust to an available proxy estimate. It is interesting though, because it shows clear intent of "we don't want to show actual sentiment".
The official youtube stats (views, comments, upvotes) are not real/real-time either. But that's the best we have. And dislike numbers are in the same universe of credibility and closeness to reality. It's definitely good enough.
If you want downvote data be more precise, do your part and install the extension! :-)
