And can make things far more complex too. You now need people to understand both ipv4 (for your public facing) and ipv6 (for your internal ones).

Instead you could just choose ipv4 only and reduce a lot of complexity. Sure there are also downsides -- if you're in a large org and are running out of RFC1918 space, or you're rationing it to smaller than /24 networks, that can be a pain (I don't see a benefit of more than 256 host addresses on a subnet as that's already far to large a broadcast domain)

Obviously. I thought it was clear enough that I was takling about public-facing servers, since I talked about the capabilities of users' devices.