for accounting reasons, there are no classic swaps in football, and even if there was any, a valuation should be declared anyway. remember the caldara-bonucci "swap"? valuations were very similar, but two separate contracts were made. same goes for the spina-pellegrini, cancelo-danilo, pjanic-arthur deals. legally these are separate deals with their own terms, and a valuation always comes with a contract. even the payment terms are defined separately.
if the clause still exists, the only way to "trick" boca would be a double sale. sell both rugani and bentancur to atleti. their market value is let's say 2m + 40m, their contractual value could be different though: we sell rugani for 40, bentancur for 2, boca get 1m. (and never deal with juventus again lol) this is shady af but legal. never gonna happen.