Voivod's "Nothingface"
I challenge anyone with a decent knowledge of progressive rock bands like Rush, Yes or King Crimson to listen to Voivod's "Nothingface" & hear anything that shouldn't be categorized in the same fashion. There really isn't any metal left by this stage so I'm proposing that it be tagged as "Non-metal".
This is a tough one since it absolutely skirts right on the edge of being punk/hard rock rather than Metal. Using your comparisons of Rush and the even more progressive Yes though I think Nothingface still belongs in the Progressive Metal tag.
Although the riffs and vocals are definitely more Hard Rock-centric, the Thrash influence is still definitely noticeable in the bass, drums, and the overall tempos and feel of the songs. Zero songs on Nothingface have that free-wheeling Rock n' Roll impression because of the chug of the bass, slower double bass drum, and the overall dissonance of the minor keys and chords. While certain parts of it may have zero metal, like the beginning of "Inner Combustion" and the verses of "The Unknown Knows", there's still a darkness and slight aggression of the entire product that I think can only be categorized as having Metal influences still.
This release has been added to the Hall of Judgement.
I've decided that a YES 1 NO 6 tally is close enough to a consensus on this one so I've denied my submission & "Nothingface" will remain in The Infinite under the Progressive Metal genre.