Thank you soo much man, cheers!You can define the rain physics parameters manually on any tire and then it won't use guessed ones.
For moving water it's the tread specs:
[FRONT_0]
...
TREAD_COVER=0.20
TREAD_DEPTH=0.005
first is fraction of the tread pattern that's gaps (so .20 means 20% gap, low corresponding to a race tire) and depth is how deep the grooves are, this is a pretty typical 5mm