Strongly disagree here. Sponsors give a name player a fixed sum and usually a certain amount of product which they can sell. They do not give them tournament participation costs.
Other than the matter of future contract negotiations with their sponsor, a player's participation decision, tournament by tournament, is an independent financial decision. That said, if a clause in his Meucci contract requires a pre-specified level of WNT participation, which is unlikely, then there is a possible breach of contract.
So no, it is not a sponsor's obligation to either pay a player's tournament participation costs or to monitor things like eligibility for invitational events. It is their option to do so if they are so inclined, but Meucii doesn't look bad here on any level.