I should try to distill the broader point that's driving the back and forth from my end a bit(which is more macro than about JD's words specifically), because I don't have particularly strong feelings about Perlaza. If they bring him up I hope he hits and sticks, and I doubt they'll jeopardize the development of anyone I think deserves it more to do so in that case. I also don't think much of his future impact, without more cartoonish AAA performance or other pedigree there's not much reason he clears the high bar to be a significant contributor with where he lives on the defensive spectrum. As such I don't think there's much urgency to make irreversible decisions(cutting Mancini, adding Perlaza to the 40 man) to facilitate his 2023 debut.
That said, I think a lot of fans(some who I respect their analytical thinking, like Brett/Bleacher Nation) have fallen into a trap in how they think about the deadline and remainder of the season. It starts with the buy/sell binary, which in this situation has never made sense to me. Jed has set the roster to continue to try to be competitive in 2024-2026, and he almost certainly doesn't have the job security to blow it up and start over. You see this in last year's deadline where despite heavy rumors he didn't do anything but trade a few relievers, and one of those was for an immediate contributor. Add in that there's about 3 teams that are looking to trade away any quality outside of rentals and the likely outcome is a minimal trade market or one that the Cubs participate in at both ends in searching for 2024 contributors.
The related issue to this is fans have not only been conditioned into that buy/sell binary, but that August/September is an open tryout for new contributors once you've stripped the roster in your Sell-off. There's nothing wrong with the idea that post-deadline you prioritize some things differently, but this gets warped into the idea that anyone currently on the fringes of the roster has no use if they weren't able to fetch a prospect at the deadline. There's plenty of marginal roster players who could have a 2024 role even if they had struggles in 2023, and it's far from certain that casting them aside just to make way for a player with limited ceiling is the right way to maximize your talent to be the best you can be in the short and long term. This is magnified in Perlaza's case by him being a defensive zero, because he has a higher bar to clear to be useful and more competition for the spots where he could fit in. Mastrobuoni, Wisdom and Madrigal(all of who are hitting well at the MLB level most recently and exceeded Perlaza's AAA line in limited time there) can be similarly useful as a good Perlaza outcome without unexpected leaps at the plate thanks to their defensive value, and players with greater pedigree and ceiling(Amaya, Morel, Mervis, a potential deadline acquisition) sap potential opportunity along with starter incumbents(Happ/Suzuki).