IPv6 only bound services accessible from IPv4 on dual stack Linux host: how does it work?

I have this situation where Apache is listening on :::443 only
on a Linux host that has both IPv6 and IPv4 enable.

I can access the content served by that Apache from IPV4 only enabled computer.

Can someone help me understand what's happening, and how to verify this configuration on a Linux host (CentOS in my case)

I read somewhere that

[...] servers bind to IPv6 addresses (on all interfaces or on a specific one, if needed) and treat IPv4 as mapped ones because IPv6 and IPv4 share the same port space on the same machine. This works transparently thanks to glibc and is a recommended way to write networking applications. See man ipv6(7) for details.

I'd guess this means the only way this could happen would be with Ipv4 mapped address. However I can't get this working with ping6 ::ffff:127.0.0.1 or to my public IPv4 address.
Besides I don't see any config that would support this when looking at ip a