This is an important point. The OP words this incorrectly in the thread title and the meanings are quite different. Having a child that is in a sport and hoping he/she can succeed at a pro-level, is a lot different than being convinced that little Johnny is going to be an NFL QB.
Yep OP is editorializing. The article is editorializing too, especially "Those parents are deluding themselves". "Hope" and "delusion" are in some ways synonyms but they have very different connotations. The article doesn't really motivate reframing the former as the latter.
And why is 26% "astonishing"? Hope is cheap. I'm frankly surprised the number is so low.
It gestures at how hope could be a problem (sports can be expensive) but doesn't really close the loop. Hoping your child goes pro is only a problem if you're making sacrifices to pursue that hope. If the kid wants to play and is good and gets value (social relationships, exercise, personal achievement, etc) out of participating, then hoping it goes into a career is just idle imagining and not a driving "delusion". So: how many parents are making sacrifices chasing an enterprise doomed to fail? Do such parents have access to an alternative investment they could be making?
The article even recognizes it's doing this, concluding "As students and families sign up for sports this fall and winter, we should be asking: if you knew this was just for fun, would you still do it? Would you do this much of it? Would you do it differently?". You can easily and all of those questions in a positive way (would still do it) and also hope your kid goes pro. Those aren't exclusive. The gap between hope and achievement is naturally large. That's the whole thing with hope. Are parents misled or misunderstanding how long their shiots are? The article doesn't demonstrate that.
So like. The article poses a question worth asking but doesn't really offer enough evidence to draw any useful conclusions.