Honestly, if you're not getting unlimited PTO at this stage, it's a dub - especially at a major holding company. I recently started at Publicis and several colleagues who came from WPP weren't fans at all.
For context, I had an interview scheduled with WPP that they never officially cancelled - just never called. Then they sent an updated invite after the call was supposed to start. By that point I'd already accepted an offer from Publicis, and it took another day or two before the original recruiter reached back out asking when I was free for another chat. The person I was actually meant to speak with never tried to communicate, and they weren't even the same person I'd connected with on LinkedIn.
That whole experience left a bad taste about WPP's process. And I know this thread's about PTO, but those vacation dates are pretty much standard across all agencies anyway.