Probable comment vote bug in late answer review list

When reviewing a late answer, I scrolled down to check the question, to get some context. This question had a lot of comments, and the show x more comments link was available. This of course lead to the entire comment list of the question being shown. But it also allowed me to up-vote a comment in that list. Which lead to the I'm Done button getting activated.

In case the question's entire comment list is already visible (i.e. the show x more comments link is not available), then voting on comments is not allowed.

Isn't this a bug? If I'm reviewing a late answer, why should a vote on a comment in the question be counted as reviewed?

Sample post

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