yeah, and I would wholly relate those bands. Anything that leans closer to rock/pop could be tied together in the progressive scene. There's the RIO bands that take the avant-prog title, but their music sounds quite different from the usual prog-rock arrangements.
I would recommend you check out Autumn - Oceanworld. It was a group that only made its mark in the late 70's, when people generally stopped caring about complex instrumentals. As far as instrumental prog groups go; this is a gem. They strike a distinct balance between classical composition elements and rock without leaning into the avant-prog territory. As far as musicianship they take the cake for me.
https://www.youtube.com/watch?v=dp76oXaT6rI