God there is some crap here, and the sound of elastic being broken as knickers get in a twist..
Progressive music in the 60's was a variety hybrids of rock with other musics, which had not been brought together before, and the more successful bands generated a synegism of original sounds. Fusion in 1965 or even before meant jazz fused (or hybridised) with other musics - the first with Indian ragas i.e. with various Joe Harriott/John Mayers Indo-Jazz Fusion groups. Specifically jazz rock (fusion) was developed independently in the States at the same time, and it as been recently suggested that the likes of Georgie Fame, or Graham Bond were playing jazz rock in the UK as early as 1963 - although their music then more definitely in keeping with the R'n'B club scene.
'Fusion' and 'hydridisation' are synymous in the English language, but fusion wrt to music has come to mean jazz with some other form of music. Alas terms stop having their literal meaning in music many decades ago, and here at Progarchives there is a confusion as to whether terms used to categorise, should be employed literally or otherwise. Sorry remember we are stuck with some unfortunate historical conventions. So unless we are dealing with rock music with a significant proportion of jazz, fusion used here at Progarchives is an ambiguous term and not consistent to its use outside of Progarchives. Therefore use of fusion here is often very confusion and wrong. I suggest we get rid of it, unless used in full as jazz rock fusion.
The specific case of TMV: the band has progressed in the literal sense by hybridising musics not normally found in traditional progressive rock. Indeed there are distant and brief echoes to Mahavishnu Orchestra, but too little to park them in the jazz rock - neither would you do that to Yes, even with Tony Kayes jazz-and R'n'B flavoured Hammond or Bruford jazz influenced drumming.