It's a corvette. Why it says frigate on the first page you link, I don't know, but it's a corvette. The description for the rest of the page never mentions it being a frigate, only a corvette. It USED to be classified as a frigate, I guess.
It's considered an escort because it doesn't fall into any other category clearly. It's no gunship, it's certainly not a cruiser, etc. The model should be listed as decommissioned, even though it remains in the Type 29 Fleet Plan.
And yes, the first page you link to is the most current one, the one where it has more modern weapon pods and a faster CDD speed.