My understanding is that a new Assured Tenancy comes into existence when there is an LSVT, so you can rule out old schemes and even older schemes.
I am sure you know this bit, but by Para 11 of Schedule 2, these tenancies are excluded from RO referral unless there has been an increase in the rent since disposal and you think the new rent is too high. You cannot refer to the RO on grounds of under-occupation, however, if the disposal was made after October 2002.
Having decided to refer to the RO, you have made the claim into a regular plain vanilla LRR case. If you don’t refer to the RO, you cannot restrict in any way at all because to rely on Reg 12(7) and yet not refer to the RO is, I think, logically impossible.