He had a release clause that expired on a certain date. SAFC didn't match the amount specified in the release clause by the specified date. That isn't a 'grey area', that is very clear.
Football is different because, in addition to the contract of employment between employer and employee, there is the requirement for players to registered with the national FAs, EUFA and FIFA. Even if Lucumi refuses to play for Bologna again, SAFC couldn't register him as a player, because Bologna would retain his registration until the expiry of the contract.
Lucumi may now regret signing the contract and also agreeing to the inclusion of an extension clause that could be triggered unilaterally by Bologna. Notwithstanding his regret, he did sign it and is now stuck with it.