Hikvision ANPR and Fps for /P a non /p version DS-2CD4A26FWD

I have bought 2 cameras for license plate recognition and i have notice differences with Fps:

in model DS-2CD4A26FWD-IZHS/P i can set 50FPS
but in model DS-2CD4A26FWD-IZHS the FPS is limited to 25 (Firmware version: V5.4.5 build 170302 (latest as on Hikvision newsletter of november)

I can't find information about this difference.
I know that with /P the model is for ANPR, but also without /P the ANPR is available and working.
If in the model wihtout /P i set "Smart Event"...

Hikvision ANPR and Fps for /P a non /p version DS-2CD4A26FWD