The multis were available, to my knowledge, for these albums (at least the vast majority of them); Dan Bornemark even had the complete multis for The Missing Piece.And I could be wrong, too, but I am quite certain the multis weren't available, as it's been three years since Three Piece Suite was released, and nothing until last year's mega box. They released PatG in 2014, Octopus in 2015, then nothing (as I believe they were looking for other multis) until the incomplete compilation, Three Piece Suite In 2017. My understanding is that compilation happened because original multis for the first three albums were unavailable.
So, and again I could be wrong, I believe that the multis have surfaced since then...either way, its GREAT news!
It took some time because they wanted to remix and release the more popular albums first.