OpenVPN on phone - DNS only?

Never seen this before. OpenVPN on phone. Won't connect using IP address, but it works fine when using a DNS name?

Can use web browser to enter an IP address to the VPN server, and that works fine, but must use a DNS name for OpenVPN profile / endpoint? Had static IP in the exported profile, which fails.

There is a DNS entry, but have never needed it on Verizon, AT&T, and AFIK, T-Mobile. The profile always just had the IP address, and "just worked" on every other cell carrier I've tried it on.

Not sure how this is possible, but at least it works now. At first, I was dreading that Sprint was blocking the (non-standard) port for the VPN.

Maybe this is helpful for someone else out there. Found it strange.