The point of the argument is that in the old days you didn't have to buy anything extra; you could tinker with your main computer. This drew in some opportunistic hackers.
You realize that mass adoption of the "home computer" is a very, very recent phenomenon, right? I grew up with a computer in the late 80s/early 90s because my father was in the field, but most of my neighbours did not start getting computers until the mid 90s. IMHO the image of the precocious youngster learning to hack on the machine his family just happened to have is a bit of selection bias.
People look back at the wonderful days of the 70s and 80s with rose tinted glasses - the truth of the matter is back then computers were exclusively hacking machines (i.e., you couldn't work them at all without some fairly in-depth knowledge), you did buy them just to hack on it.
So yes, many precocious youngsters of my generation learned to hack just because they happened to have computer (bought for non-hacking purpose) and it was tempting and possible to tinker.
So, the only people that bought an Apple IIe were tinkerers already? What about the example of the father that bought it for the word processor? Is that example entirely unreasonable or blatantly false?
What about the Commodore 64?
I was bought a Spectrum as a child (and saved up christmas money for an Amiga). My parents weren't at all technical. I learnt a bit of BASIC but not much (I didn't have the patience to program much), but I did get a decent understanding of what went on inside. So I was happy to build my own computers.