Interesting question.
I'm not surprised that Fripp was blown away, I think they all knew who McLaughlin was and were following his playing. Of course Mahavishnu was the next step for him.
I also think Mahavishnu was probably a bigger influence on ProgRock.
I kind of wonder about Yes and/or ELP. Yes was too structured for any real improv, Relayer has it's fusion freakout section - but it seems composed. If Keith Emerson was influenced, he never showed it.
Any other bands that were or could have been influenced?
Henry Cow - doubt it.
Gentle Giant - don't think so.
the Mothers and other Zappa bands - not obviously so.
Pink Floyd - not much of a Jazz influence at all...
the Canterbury groups - not from Lifetime...
most of the Jazz influence on ProgRock seems to show up in one chord jams, from Kind of Blue, maybe?