Penile inversion is the oldest technique, the penile flap is more suitable for construction of the external lips to match the nature one, but this material is not enough to create the lips in the inversion technique, as a result, later vaginoplasty surgery usually necessary to improve appearance, but the result is not as nature when constructed with penile flap. Present technique of non-inversion is using normal skin graft for vagina, the new technique simply change the graft material with cheek cells which is better, so the rest of the technique already exist as standard procedure (not entirely new).
Cheek cells can apart from being self-lubricating, it can also absorb sexual fluid that is left inside, which mean it is self-cleansing like the nature vagina, later administration of hormone tablet can be through this route too (thus by pass the liver).