It is. What's the difference between a shot saved by the keeper and one saved by a defender? Fuck all. Yet the first one counts as a shot on target, the second one doesn't.
And of course with deflections it's up to the person recording them to decide.
If a team was to have 15 shots and 15 of them were blocked by the defending team, you would say that it was a great defensive display.
If a team was to have 15 shots and the 15 of them were on target, you would say the defending team got battered.
It's a huge difference. Not only are you making the keeper work but shots on target usually reflect chances created.
And as for deflections, it's not just up to the person recording them. If a shot is deflected onto goal forcing the keeper to make a save, it's a shot on target. If the shot is deflected out of play, it is a shot off target.
I find it odd that you're dismissing such a vital and tale telling statistic as shots on target when it tremendously coincides with how we have played this season.