I think it's much more likely that what you're seeing here is patients with very mild cases (in last year's outbreak) not being accurately reported/counted.
This is a writeup of only known cases, in an environment where many who refuse vaccines see themselves as anti-establishment (and understand that their position isn't in alignment with standard medical recommendations... hell, in some cases it seems to fuel their persecution fantasies).
I'd bet money that lots of anti-vax parents whose kids had mild cases didn't report them to anyone outside their own social circle, and certainly not The Medical Establishment (TM). I'm a little surprised that so many non-hospitalized cases were actually reported.
What you seem to be advocating for, btw, is a return to hundreds of easily preventable children's deaths annually. Even the "safer" stats you pointed to (e.g.
here) point to 400-500 annual deaths, 48k hospitalizations, and 1,000 cases of encephalitis,
as a fraction of the population in the early 1960s.
The current US population is roughly 340,000,000 (vs. 179,000,000 around 1960, very roughly). So assume nearly double the number of easily preventable deaths, hospitalizations, and cases of encephalitis per year, mostly in kids.
That's still rare enough for any one individual to feel like "it's not so bad," if you don't look at population-level data. But the population data is readily available. I'm going to go out on a limb here and guess you were a kid in the pre-vaccination days, rather than a parent worrying about your own kids' health.