That might be the case in sharpness and CA, but it's still only 22mm vs 19mm! And when you're shooting interiors or architecture, that 3mm means a great deal (wider = specific purpose lens)

Due to unusually high aberrations in the D-FA 645 25mm (designed around full-frame 645), the lens was re-released as a DA 645 in North America with a longer lens hood for the digital 645d + z, but only North America! Everywhere else got the older film version lens...

Now it looks like all versions (confirmed with B&H), that the 25mm in all versions has been scrapped in favour of the 28-45.
A big loss for the Pentax 645z, but a big win for those who have the 25mm and sell secondhand.

Sorry, but DA 25mm is also gone, just check out B&H
http://www.bhphotovideo.com/c/product/852725-REG/...

I believe Ricoh/Pentax have scrapped this lens altogether, in favour of the newer 28-45mm... As to the reasons, who knows what Japanese old business men think! (Lived in Japan for 3 years and they're strange creatures)