Demonstrated as stated is just that but I do not for one moment think that is realistically the case.
It is surprising how many 15 18 kt days there are
What happens if the aircraft is tested on a 25 kt day is that the figure the pilot puts in the book? I doubt it!
There will no doubt be a discussion and I am sure a lower figure would be selected depending on how tricky the aircraft was at 25kts.
The overriding consideration will be a fairly low timed PPL who does not fly that much while not selecting a figure which makes buyers think there is something wrong with the aircraft.
15kts will probably be used as a bench mark. If its tricky in wind the aircraft will be set lower if its good in wind a few kts higher!
Also into consideration will be the target market and experience of the pilots who are likely to fly the aircraft
Pace