An AR-15, a Remington 870 and two Glock .40S&W pistols don’t exactly strike me as a collection every enthusiast would have. Seems kinda... sparse. And not terribly expensive - he spent less than $4K on all of it, assuming he paid retail.
I thought it was a Glock 9mm & Glock .40, but, regardless.
It seems the guy did the research on the _first_ firearms anyone should buy, and those are the makes/models/calibers you’d see recommended for such a person.