Any AR that’s not a .22 and MAYBE 9mm requires the “buttstock” or at least a buffer tube w/ buffer and spring. Pistol models have shorter buffer tubes, but they’re still there. Otherwise, an AR will not function w/ a folding stock.
While that stock would be legal on your preban as long as it meets minimum overall length (26") requirements, but would not function.
Also: You can have a folding stock on a semi-auto as long as it cannot fire from the folding position, pre or post ban.