Very true, and as annoying as it may be to Ninja who could have negated the knockback by 0ing its damage, I suspect Shadeshift remains as it does primarily because it's a compromised version of Perfect Dodge, which obviously couldn't work on spells, either. But, it's not as if XIV's afraid to cut its history loose whenever they feel like it, so it could go either way.
To me the real question is whether NIN deserves this boon relative to Monk, Samurai, and Dragoon. I'd argue not, especially if it could merely see a CD reduction to Shukuchi.