Exactly! I have seen that too! Very nice implementation of wet grip there.
As for tire deformation not been there, I agree that maybe it's the reason for not realistic grip levels of different tires in GT5
but: I support the view that the actual difference in grip level between different vehicles with same tires doesn't actually appear when doing constant circles at 50kph but when squeezing them around a track on the edge. Then you can compare the level of grip in same corners. The balance of the chassis in conjunction with the weight and the suspension settings and the aero appear under high pressure. There, the ability of a vehicle is definitely judged.
A car magazine here in Greece compared 10 or more sports vehicles 7 years before and found out that on
Serres circuit, Mazda RX8 had a max grip level of 1,18G - same as Lancer Evo8 MR (EU model). What tire must put on it in GT5 then? RH maybe? No, because if you take it for a ride with SH or SM on it, there are some fast corners that may reach this level for some tens of a second. So?