Usage % is kind of a misnomer, as it is specifying the amount of processor cycles are being used, rather than how much of the silicone in the hardware is being used. You can have a really inefficient and heavy operation that uses a tiny part of the hardware, but eats up every processor cycle, and have 100% usage with barely any thermal output or power draw. For example, writing a small script that reorganizes an extremely long list of items can use every processor cycle and bring the system to 100% usage, but it is only operating a small portion of algorithms on the processor and not actually using a lot of the hardware. So that 100% usage is likely accurate.
This basically means that the game is rather unoptimized, or at least using heavy technologies that don't use all the hardware but take a lot of time/effort to do.
At least it's not "the narwhal bacons at midnight" shit