When I first learned yokomenuchi, I often slid off the centre-line and struck nage from the side. My first sensei subsequently corrected me by saying that yokomenuchi meant moving in a straight line towards nage before chopping to the side of nage's head. I think my confusion was due to looking at ken techniques, where one would strike the partner with a bokken by moving off-centre.
More recently, one of my senseis said that yokomenuchi SHOULD be done by moving off the centre-line - i.e. not moving in a straight line towards nage. The reasoning comes from looking at kumitachi practice, where one doesn't rush straight into your partner, as you would get impaled by his bokken. In the empty-hand technique, a similar reasoning followed - i.e. you would run into uke's outstretched fingers (or maybe get punched) if you moved in a straight line when doing yokomenuchi.
I would really appreciate everyone's thoughts on this. Thanks very much.
ps I seem to be asking lots of basic questions recently... don't know if that's a good sign