zjc was picked up in the first place because EDG were still trying to lean into the same playstyle (double init) that won them champs - this is also what fan backlash/pressure has been wanting. They've finally realised that isn't going to work anymore in this new meta and that's why he's off
They have literally tried basically what you are suggesting, in their game against Trace - zjc had the chance to play recon, moving nobody off of init - and if you watched the match you can see how terribly that worked out, I haven't seen EDG play this lost since last year vs LOUD. In the past even, any time they have tried moving nobody off of init it hasn't worked well and calling has suffered - nobody himself has said he is most comfortable calling on init too.
Because of how packed the schedule has been recently, the fact they've had far more time to practice with Jieni than with zjc, and since they still need to ensure they actually make champs - are probably the reasons why EDG decided to go back to Jieni, he was the one they practiced trying new meta comps with the most and in the past - they've also been said to have been performing really well in scrims with him. And after today's game it's evident that they look far more comfortable, and aren't just randomly wandering around the map on attack.
And don't get me wrong, I was hype af when zjc was joning the team. And he still has a lot of potential, but since they're already in the split ig they'll need more time to cook with him, Jieni also used to be a duelist main so as of now he is more flexible - that can change in the future once zjc has more time to practice the other roles though, I do want to see him shine