According to Cadena SER, Antoine Griezmann and Barcelona agreed to terms for a deal in March. The deal would have come together while both Barcelona and Atletico Madrid were still each competing against each other for La Liga and Champions League titles.
The report dives into details that the negotiating began between the two parties last November. The timing of this would be pretty insane, given that Griezmann told everyone that he was committed to Atletico Madrid last summer. That would mean within a few months Griezmann moved from being committed to Atletico for life, to negotiating with Barcelona.
Barcelona and Griezmann are already on thin ice given that Atletico reported Barcelona to FIFA for their discussions with the Frenchman last year. If the timeline lines up, then indeed Atletico would have complaints and they would certainly be valid.