You are basically correct in the perception that a DV that explicitly disputes the validity of the debt can be contradictory in its implication if it also requests a PFD agreement.
A timely DV that disputes the accuracy of the debt, in whole or in part, imposes a cease collection bar on the debt collector. FDCPA 809(b).
That thereafter prevents the debt collector from collection activities until they have first sent the requested validation.
That includes their ability to negotiate payment of the debt.
Thus, including both a dispute of accuracy of the debt and terms for negotiation of its payment can create confusion.
If your communication is intended as a PFD offer, I would leave out any direct statement that you dispute the debt.
Language such as not admitting to the debt, but willing to negotiate payment to resolve the matter is fine.
Clear dispute of the accuracy raises legal issues that should be avoided......
