I think the issue is less about the actual payments, but more to do with the WICB flip flopping and going back on their previous agreements again.
I don't think that's what's happened.
The participation remuneration for a contest organized by the ICC that the players participated in was $100. They negotiated a contract with their board for a 25% cut.
Now the ICC changed everything up and said that the boards would all still get $100, only that it would be split into $20 a year over 5 years under a different heading of "member's contribution".
Their contract was for the splitting of participation remuneration, not member's contribution. Therefore legally the contract they signed with their board is now just a worthless sheet of paper. That participation remuneration does not exist anymore technically.
The WICB, in a 'gesture of goodwill' says that the $20 they get this year is the legal successor to the participation remuneration thingy, and so 'honouring the previous contract', gives the players 25% of that, which is effectively $5, an ~80% reduction.
The players could still make as much as before by continuing to feature in the teams put out by the WICB, provided they continue to receive the 20% of that ICC contribution every year in the form of annual contracts. It would now be an installment scheme instead of a lump sum payment. That would require a committment from these players to Test cricket, and not just concentrating on a single hit and giggle tournament, which might not be palatable to T20 players for obvious reasons.
What we don't know is whether it's the T20 squad being disingenuous and hiding that fact (notice the lack of protests from the domestic players and Test specialists here), or the board refusing to pay out that remaining $80 by resorting to perfectly legal accounting tricks 101.