Yes, that applied to everything but his lead guitar tracks. And he was a master in the studio, as you know.
Zappa recorded guitar solos in the studio. I have followed him since his 1st album. All that early stuff through early 1970s was done in the studio including his solos.
Later on after he had the technology to multitrack recordings all his live shows and get clean recordings of his guitar solos — be began the mix and mash technique of mining his guitar solos.
He recorded the early shows as well but there was less ability in the 1960s to capture individual guitar solos as the recordings were 2 track and later on 4 track etc.