I suspect it would have been marketed for what it was . . . Jan returing to the studio, and returning to arranging and producing new music, while recovering from the accident.
It would have been seen as a foundational stepping stone to Jan's solo recordings in the '70s, when he began to sing again; and also continued to write, arrange, and produce original compositions (released on Ode and A&M).
Glen Campbell became a huge star just a few months after singing on Carnival of Sound; and this would only have helped the album's profile. Ron Hicklin and Tom Bahler were all over the Partidge Family records (for example). It would have been appropriate to publicize the studio singers, given how the album was recorded.
Similarly, if Dean's album had come out in its time, it would have rightly been seen as an attempt to keep the J&D name alive while Jan recovered.
They really mishandled that whole situation — which is very clear now with the benefit of hindsight. A golden opportunity slipped away.
In a perfect world, Dean would have accepted the counter-proposal for releasing Save For A Rainy Day on Columbia — putting J&D in the thick of things in '67. That deal would have put Jan's new masters in the hands of Columbia, paving the way for a follow-up produced by Jan — with music that ended up on Carnival of Sound — and Dean would have been a vocalist on the follow-up. And they may well have altered the track line-up.
Had things gone down as they could have, Screen Gems would not have pulled the plug on Dean's material; and Dean would not have had to release "Vegetables" under the name Laughing Gravy. It could have been credited to Jan & Dean — in the same spirit as Save For A Rainy Day.
The above scenario would have given J&D a solid presence in '67 and '68 — a really important time in pop music. It could have been a big springboard for Jan's recovery, and J&D's continued collaboration as artists.
But, compounded by Jan's new challenges, their relationship at the time was simply too strained for them to work together. And they both lost out, as a result.
Very damaging set of circumstances.