Hi John,
I've always used "english" to describe left & right spin, anything on the vertical axis was not labelled as such. However, it's just the way I was taught to describe the cueball hit - but you are 100% right that once you leave center, all spin principals apply. So with that said, you are probably right.
Regarding tangent line or how the cueball leaves the object ball, of course high & low "spin/english" will have an effect on the direction of the cueball overall, but not at the point of contact, the alteration takes effect only after the cueball has enough time to bend. Note the 30 degree rule: if the cue ball is rolling forward when hitting the object ball, it will go apprx 30 degrees vs 90 degrees following the tangent line if it was hit with a stun stroke. So functionally, yes, "english/spin" does have an effect.
In addition, I believe that left & right spin can alter the path of the cueball also. Not changing the path from the actual contact point, that does not change, but because that contact point would be different than a center ball hit to make the same shot. The side spin throws the object ball slightly so you can hit it fuller or thinner than with center ball. Plus the path of the cueball is slightly different because of swerve or whatever you want to call it.
I hope some of this makes sense...it's late for me.
Dave