One of the big advantages to modern operating systems like Windows (XBox) and Linux (PlayStation, though technically it's BSD but we're gonna ignore that) is it separates the program from the hardware enough that so long as both machines run the same OS, the software drivers for the hardware have the same interface, they can run the same programs*. This is helped by the hardware running the same kind of CPUs and GPUs so the only piece of variability left is performance.

In the olden days, where companies would make specialized silicon chips for custom graphics processing, the OS, drivers, and driver interfaces were so specific to the hardware you had to use something like a devkit

*I'm wildly over simplifying, there are some edge cases to this but it holds true for the most part

If they're developing it for both PC and consoles, it's probably more efficient to do most of the day to day testing of new features and bugfixes on PC.

Of course you'll also have to test each platform individually