do not use your tv cable to adjust shift points or shift feel.
In an ideal world, perhaps, but I've done it on at least three of my cars over the years.
1991 Beretta (tweak the feel and shift points)
1979 Camaro w/ 700R4 (ditto)
1996 Honda Accord (tweak the shift feel; ECU controls shift points)
BUT, I don't allow the shifts to get sloppy or the clutches will be damaged. I pay attention to the transmission's behavior.
Now admittedly, the way to change the shift points is by changing the governor, possibly with changes to the springs in the valve body.
Of course, if one "tightens-up" the TV a bit, it may get "reset" back to its former setting the next time the throttle is wide-open. And then, if then the resulting shifts are too sloppy, it's likely time to take remedial action (work on the transmission).
On the Beretta, pulling the cable a notch or two tighter was akin to "sport mode" shifting.
On the Camaro, if I'm just out for a ride I might loosen the cable a notch to mitigate the neck-snapping shifts (the trans was built to live behind some power, so the line pressure runs high to give it fast shifts). If I'm out to have some fun, I'll set the cable "as it should be" using the method you described, and chirp the tires 1-2 and 2-3.
On the Honda, the shifts were just too harsh as-delivered new, so I backed off the TV just a
bit.