The problem comes with the Test wording. It's quite possible, probable even, it's supposed to be intended that legs do work for base movement speed, but as it's written it doesn't. Technically by the wording you wouldn't use the Strength in your cyberlimbs for Recoil, and the only reason you would use it for Damage is that it's part of a test (limb was used for the test so you use it's attributes sort of thing). Feels very much like it wasn't intended to be that way, at least to me.
Actually, I just re-read the section on cyberlimbs. The copy I have doesn't seem to say that they can't count for Phys Limit, only that you use the Attributes of the Limb for tests with that Limb or the average for tests that use more then one. And the section on Enhancements to them specifically uses two +3 Strength Enhancements as something you can't do, not because it would be more then +4, but because it's two Enhancement upgrades to the same stat. I am now more confused then I was before, because by this reading of it, using the Cyberlimb Attributes for Phys Limit with tests that use that limb seems to be RAW. Or I'm really out of it.