This can only be true for consumer-grade stuff. Even then I just guess the manufacturers kind of cheap out.

I have a dumb-ish Samsung Hotel TV / commercial TV at home. It has DP.

I want a TV with DP. Do you have a recommended source for where to pick up commercial TVs?

I live in Germany and I got mine from https://www.visunext.de/

Which is kind of funny. At least, to my mind this has associated HDMI-only with the budget option (TVs), and DP with the premium tier (monitors).

I'm pretty sure TVs go higher in price than monitors - although professional monitors do put up a fight.