Actually, if it had, Beefheart's subsequent releases mightn't have come as any great surprise and the appreciation of Safe As Milk as a rare work of accessible genius might have been considerably enhanced.
In that regard, a recent article in Mojo #196 makes interesting reading. John French (a.k.a. Drumbo) wasn't a founder member of The Magic Band but climbed aboard that unstable conveyance in late 1966, and was there through Safe as Milk, Strictly Personal, Mirror Man and Trout Mask Replica, though French was ejected soon after the album was completed, left off the album credits and conspicuously absent from the photos in the artwork in spite of the fact that he'd played a significant part in transforming Beefheart's musical ideas into something that the rest of the band could play.
He was back for Lick My Decals Off, Baby and The Spotlight Kid, and thus has a fair handle on what went on through the classic incarnations of The Magic Band.
One point that French makes in the Mojo article is that Beefheart wanted to play music, not work at it and it's this factor that seemingly distinguishes Safe As Milk from the later material. If he didn't want to work at it that, in turn, meant he was disinclined to rehearse and polish, and that responsibility needed to be passed on to somebody else.
For much of the later period that person seems to have been French (I haven't read too widely on the details of all this, but French's Beefheart: Through The Eyes Of Magic, a massive tome of some 900 pages (!) would presumably go into the ins and outs of the process).
That attitude to rehearsal (and the writing process) stems largely, according to French, from the fact that Beefheart started as a visual artist rather than a performer and his first attempts at playing music had involved basic blues with predictable changes that wouldn't have needed a great deal of rehearsal anyway.
I also get the impression the man was capable of producing material that was (almost) fully formed at the snap of his fingers, and that once it had been created it was finished, and there was no need for too much subsequent polishing. Trout Mask Replica was, according to Beefheart, written in a single eight-hour session and he reputedly described his creative process as going to the bathroom.