I’m not sure what your point was, but entirely covering the knees is halachah. Tefach is regarding krias shema, and hair covering according to R’ Moshe (which is misunderstood by many, as an aside).
I’m going to hijack this thread to ask the following. What is the source that a women must cover in public, that which needs to be covered for a man to say Shema in her presence?