I agree with Valkyrie Addict...Remember towards the end of DYRL (once the get into Bodolzaa's fortress) when Hikaru's Valk salutes Misa, turns, and then (PRESTO CHANGE-O!) suddenly, it's a fighter. Or the fight between Isamu and Guld in Mac+. Or almost any scene in Mac Zero. Heck, even in the SDF TV Series, there's that oft-reused shot of the Battroid going into an explosion and coming out a Gerwalk.
As far as I can tell, the only slowly transforming Valks are the Mac7 ones. And even then, it's only sometimes, in order to pad out the episode by reusing the same transformation footage over and over.
So, no, I'm not seeing how the VF-25 transforms too fast, either.