The radiators are significantly smaller than the PV arrays, but not by a massive ratio; looks like about 1:3.6 based on the published area numbers that I could find.

It looks like the ISS active cooling system has a maximum cooling capacity that could handle the equivalent of a single-digit number of racks (down to 1 for an AI-focused rack).

The heat load of the ISS is a handful of astronauts and some equipment and whatever it absorbs from the sun. Not an entire data center or a nuclear rocket which is where the radiator discussion comes into play.