Corporate's is still the five piece, hence why ITV Studios' endcap didn't change. The three piece one is just the ITV channel's logo.
On the whole, I think this is a decent refresh, but I also find it disappointing because it feels like they've forgotten about little details which make it all seem a bit of a muddle. If the above point about the five bit logo being the corporate logo and the three bit one being the channel logo is true, they've done a bit of a slapdash job of implementing it!
For example, they still use the five piece logo going into Good Morning Britain, and the sections of the logo still fade in and out (as in the previous look). ITV weather still uses the five piece logo and even retains the colour picking effect at the start of forecasts. On itv.com the five piece logo remains for ITV shows - the ITV channel page even uses the five piece logo and one of the old idents as a header image! And I'm sure there are other examples where things from the previous look linger on.
In 2013 they did a really lovely job at a comprehensive rebrand and addressed everything, ensuring it all matched up wonderfully - this time around they've slipped and not thought about these details.
The website clearly just hasn't been updated yet.