What's the purpose of that remark? They are different protocols, you can't just rewrite addresses like NAT is doing. Sure, there are things like NAT64, but that's more than just NAT, it rewrites the whole protocol headers. And it's pretty limited, all it can offer is to route to IPv4-hosts from IPv6-only hosts. I wouldn't recommend starting with something like this.
It's roughly 10 years too late for that to be a valid argument. IPv4 address space is exhausted. There are already lots of hosts on the internet not reachable with IPv4 any more. Most of them are just clients or at least not relevant for "the web", but that's subject to change as well. My practical example are the official FreeBSD builder machines -- only relevant if you're working on ports, but if you want to read a full build log of an official package build, you already need IPv6.
An ISP only offering IPv4 is an anachronism. In fact, I see much more the opposite problem: ISPs only offering IPv6 (plus some "crippled" IPv4, typically in the form of "DS-Lite", where for IPv4, a tunnel is established to some router operated by the ISP that does NAT, so many customers can share the same public IPv4 address). The simple reason for this is the price you pay for public IPv4 addresses nowadays.