The vesting regulations are so very old that they don't have (to my knowledge) provision specifying how they apply to a defined contribution plan with various contribution sources: elective deferrals, match, employer nonelective, QMAC / QNEC, safe harbor contributions, and possibly further subdivisions as defined in the plan document. On the other hand, we "know" (or at least its a universal consensus view) that one can have different vesting schedules to some extent for these contribution sources.
So I lean toward yes, that one can preserve the two-year cliff vesting schedule for QACA SHNE without having to switch it to a traditional SHNE. I wish I could cite a regulation that gives me 100% confidence in the answer.