It's an interesting question and I spent zero time looking for any IRS or court interpretations of this requirement other than reading the statute and the relevant regulation (no differences). But on its face, I think your clients are correctly applying the ordinary meaning of the word "and".
"Ordinarily, as in everyday English, use of the conjunctive "and" in a list means that all of the listed requirements must be satisfied, while use of the disjunctive "or" means that only one of the listed requirements need be satisfied."
Therefore, since all of the requirements are not satisfied (i.e., the one spouse does not participate in the management of the other spouse's corporation), then that individual/spouse satisfies the requirement that they are not a member of the board of directors, not an employee, and do not participate in the management of such corporation.
I know that with the double negatives, it gets confusing, but I believe that they are correct. Just an opinion though. There are instances where a court has interpreted "and" as disjunctive but those are relatively few and far between. Context is, of course, everything.
The source of the quote above can be found here:
https://www.everycrsreport.com/reports/97-589.html