Originally Posted by
Physci
The P fare is OK for me so really only interested as seems to be a quirk of the booking engine
The booking engine has lots of "quirks", to put it nicely, and yes, there are other times where you'll get different results whether you use search by price & sched or just search by schedule.
That said, some "P" fares are nonrefundable and have change penalties, some do not. You'll have to read the rules.