Folks here IMHO are suggesting that he broaden his search, not actually apply to an enormous number of schools. His guidance counselor is unlikely to be saying “pick some subset of your current list,” but rather, “don’t apply to an enormous number of schools.”
It’s totally normal for a list to see enormous movement between junior year and the last application. My kid’s tentative list (which had been highly curated by me, based on criteria she picked, starting in her sophomore year, so it included zero schools we would have been unwilling to pay for or which were otherwise unsuitable) was about 30 schools long at the start of junior year, about evenly split between safety, match, low reach, and high reach.
Then in October of junior year she decided she wanted a women’s college, and that cut the list back to five, none of which were safeties.
So she decided she was willing to compromise on a couple of wants, which added three safeties - plus she added two reaches that were not on the original mom-list (affordable but wouldn’t have been good fits for 2-years-younger her). Up to nine!
More visits in October of senior year, and both the kid picks plus five more were off the list for various reasons. (Seven schools fell off after visiting two, so it’s been slightly less crazy than it sounds.)
She revisited the one that was sounding best, said it was the one, and put in an ED1 application. In August, I’d have bet money she’d apply to 7-9 schools EA and RD, no ED school.