Even magnified it's hard to tell from that photo, but I agree that honking big blue electrolytic capacitor indicates filtering of traditional low frequencies rather than the smaller caps you'd expect for a switcher.

Still, if you're shipping PET computers with a heavy glass CRT display on top, you're presumably not as concerned with weight as you would be with smaller form factors. So this evidence doesn't bear on the article's thesis. Given that the IC controllers introduced the year before the Apple II, the chip vendors would likely have already been sending out sample chips and application notes for some time, although their target engineering applications would be for products where cutting weight was a bigger concern than cost. (Hence Boschert's company having 650 employees in 1977 and having developed products for "satellites and the F-14 fighter aircraft".