I didn't know what WOF was either; I always TEAR the fabric for borders , not length of selvedges but width of fabric -i.e. side to side, so is that wrong?

It's not wrong, but using the length assures less waving and longer pieces. There is less stretch on the lengthwise grain of the fabric (that which follows the selvege).

WOF: width of fabric, tearing is not so good as the crosswise grain which goes from selvedge to selvedge stretches so you end up with wonky edges to begin. If you want the most stable cut use the lengthwise grain. Of course more than half of the patterns out there say cut across the width of fabric. Problem is that its harder to make things line up when piecing or adding borders, or sashing.

I do it both ways - WOF and join with a diagonal seam. Why? Because it actually shows and wears less.