NFL Rules Question - Penalty Enforcement

[VA Official]

Originally Posted by FormerUmp

So even though in the double foul scenario B is the team with the ball when they commit their foul, they would still get an untimed down if the penalty is accepted?

Yes. The logic is they have a right to keep the yardage they earned legally up until the point where they fouled. Combine this with 3-3-3a, and we have an untimed down for B.