EA and Ubi have had a crossover sale agreement for a long time alreadeeeh (2013 https://www.rockpapershotgun.com/2013/02/19/lakes-boil-ubisoft-and-ea-to-sell-each-others-games/) because they ain't such fucking Nazis as Valve with regard to their stores.
By the way, the "pissing match
" wasn't so much about DLC pricing. It was more about selling DLC from within the game, i.e. EA had clickable links in their games which would take you to an EA website where you could buy DLC.
The greedy fucks from Valve disagreed with this practice, of course, since this bypassed their 30% of every sale cut cemented in their TOS. And then EA was kicked from Steam due to their violation of the TOS which they insisted on because they wanted to reserve the right to sell their
way and not Valve's way.
Steam fantards made a much bigger deal out of this than it really was ("OMG EA no longer sells games via the holy Steam platform OMGOMG!!111"). In reality EA and Valve were pretty relaxed and cool about it all