Windmilling jet engines are a typical everyday occurrence. The speed is a function of the wind direction and intensity but of little consequences to the engine itself. You can bet that the engine makers have to demonstrate this capacity even without normal lubrication. What's there as residual is good enough since the thrust loads are minimal. (just like your automobile wheel bearings)
The seizure bit is a red herring and not appropriate as an argument at these miniscule rotating energy levels.