This is not a problem although I wouldn't recommend it on a regular basis.
When hot water runs through the filtration media in a cheaper filter it creates tunnels. When tunnels are created the water can run through without contact with the media which means it doesn't get filtered anymore. We designed the UltraStream to make sure that hot water wasn't able to tunnel. We used a way of vortexing the water along with a plate inside the unit to make sure the water spreads evenly which means that the tunnels just can't happen.