Yeah and that is obviously bullshit PR. The game doesn't even look structurally different than the previous titles, it will just have more units, perhaps not even that often. Also, it's turn based, a little slowdown won't kill anyone for more version releases.
As for the slowdowns on previous systems/titles, it's the developer's fault for not opimizing them properly. I don't see how a very low-poly 3D tile-based map with 2D characters can even have slowdowns in the first place. The Disgaea serie consistently looks like it belongs to the previous generation of consoles it is on, now with 5, they bumped that difference to two generations. Graphics-wise, it looks very, very similar to Ragnarok Online, which could render hundreds of character on-screen without an issue with 1999 computers back then, which were much weaker than a PS4 (or PS3 even, or hell, EVEN PS2) is today. The game was even able to withstand several individual players spamming spells with big effects at the same time before tanking in FPS.
Pretty sure a PS4 exclusivity deal is going on under the table. Sony has been pulling that out a lot to promote the system further. I don't really mind if it's an exclusive for monetary reasons, the blatant lies is what I'm not happy with. The developer should be honest.