If it's MS, then it would put the interpretation of kakashi's whole conversation with itachi up in the air, wouldn't it?

For example:

Kakashi: <lists flaws with MS>
Itachi: How perceptive of you, I'm impressed.
Kakashi: Itachi....how bad has your eyesight gotten?
Itachi: Kakashi....you couldn't have..... (obtained MS OR realized I'm going blind)