Can't say, not familiar with the FFP in detail. Best guess, that 78 mil side pay-off would be exploiting some sort of a loop-hole in the rules.
If this were to go thru, and it seems it will, it will put the international mercato on an entirely different type of a slippery slope.
Just 3-4 or so years ago, the Bale and Pogba transfers seemed like a ludicrous amount of money to pay for a player and the likes of Messi and CR7 were getting paid 11-12 mil a season.
Now, those moneys look like pocket change already with the likes of Belotti and Morata going in the 80-100 mil range, while premier talent like Mbappe, for well over 150 mil.
And that's before this Neymar transfer to PSG, which in and of itself could reset transfer fees and salaries to a whole different level over insanity.