I appreciate the case law. Principle seems to be that for motion to dismiss for failure to state a claim, issues of law, rather than issues of material fact, are operative.
Basically, OP has not even been served, but is concerned that if served it
might be difficult to prove SOL as an affirmative defense. Some question here as to who would have the greatest burden of proof.
Best case would be that, if served, complaint on its face shows action barred.
Key to that scenario is that complaint alleges date of accrual.
I had just the experience about which OP is concerned.
Action was time-barred, but complaint lacked allegation of date of accrual.
It might not have been entirely correct, but I filed a motion to dismiss
for failure to state a claim. My reasoning was that, ultimately, plaintiff would have to allege a date of accrual to prove that the court had subject matter jurisdiction. That is a threshold issue, and the court certainly would not want to waste time on a case for which it lacked jurisdiction.
On its own, plaintiff filed an amended complaint, which alleged the date of accrual. On that basis, I was able to file a motion to dismiss because, on its face, the pleading showed that the action was barred. I never admitted to the debt. Only procedural law was involved. No discovery was necessary.
Perhaps in the case just described a motion for more definite statement would have been more correct.