Ok, here's a couple things to consider. #1 that's the way the manufacturer recommends it. #2 how fast are you really going to be riding through the rain to worry about enough water to actually cause your bike to hydroplane?? I ride in the rain all the time, and I slow WAAAAAY down. It's one thing to mess around and fishtail here and there in a car or truck, but I've only got 2 wheels and I'd like to keep them both firmly on the ground. Anyone riding like an idiot in wet conditions is bound to have the bike lay over on them.
Actually DUNLOP doesn't recommend it. Metzler does and their tread pattern is designed to allow water to escape in either direction.
There are times when you can come up on a puddle of water on a dry day at speed.
Wet riding is treturious enogh without risk premature hydroplaning compared to another tire.
That tread pattern will trap water sooner than another tire that has channels that allow it to escape. That's why I chose to run the metzler instead of running an Avon. It has the same kind if tread pattern.
If you are especially carefull in wet conditions as Josh suggests, and are warry of puddles, you should be able to do fine with it till you need another tire.