That would most likely be because the images in question weren't posted publicly until the day after CatDog and April were revealed, and Rep responded to them pretty much immediately. There wouldn't have even been time for anyone at Fair Play to have seen the leak before then, let alone alerted the Ludosity team to it.
If the leak in question is fake, I'm honestly terrified of how (presumably) some rando on the internet made perfectly accurate models FROM SCRATCH for every known character in the leak, including April, who wasn't known to be in the game until less than 24 hours prior, Ren & Stimpy, who were known to be in the game, but hadn't had their models shown until just now, Nigel Thornberry, who hasn't had an official model since the PS1 era, and Powdered Toast Man, who hasn't had a model period. At this point, the leak being entirely fabricated is honestly the LESS believable story for me. We are far beyond Grinch territory here.