Isn't the cornerstone of (any type of) Flannery responder's preference for one major over the other? (Here, spades over hearts?) If you define reverse Flannery shape as "4+ hearts, with longer spades," then: Opener corrects with 2♠s and 3♥s, and it is safe to include 6-4 and even 6-5 hands in the 2♠ and 2♥ responses. Now 1♦-1♠; 1NT-2♥ and 1♦-1♠; 1NT-2♣; 2♦ - 2♥ are 5-5, weak and invitational. Yes, responder is poorly placed with 5-5 (weak) after 1♦-1♠; 2♣. And the 5-5 is somewhat more common than the 6-4. But responder might be able to stretch and bid 3♥ if that is a natural invite for you.