It probably doesn't. Just clean it and reboot it. Aftermarket subaru axles are a waste of time, just clean and reboot the one you have.
Change all of them? no way. subaru OEM axles last the life of the vehicle, you might be throwing away great life long axles and installing crap aftermarket that definitely won't last the life of the vehicle consistently. just reboot them when the boots break.
Use Subaru OEM boots for longevity. check mounts and make sure the engine/trans aren't rocking too much and stressing the CV boots more.
if it's a lifted vehicle it might just go through CV boots quicker.