I just read an article on training/pruning apples. It said that every pruning cut visible from above is a disaster. Those strong vertical shoots can't be turned into fruiting wood by pruning. A few can be made fruitful by training to 45 angle but if more than needed it's constant pruning because they just keep coming back.

Avoid them by training shoots to 45 angle maybe a little less. Remove all shoots bigger than 1/3 diameter of the trunk. I believe they recommended stubbing back so as to get renewal growth.

The article I'm working from is GFG vol 65 #7 page 46.

In managing espaliers there is a somewhat controversial method of repeatedly pruning uprights during the growing season- some varieties apparently will spur up when you do this- the problem is, other varieties will remain vegetative if you cut into 1-year wood, which I think is the source of the controversy.

I prefer to leave the least vigorous uprights and let them go until they flower up.