That's true for most phones but the HTC 10 is one of the few phones that even Unlocked works with most Carrier specific features such as Wifi Calling and VoLTE, although in this case not even the Tmobile carrier version has the Enhanced messaging and Video Calling native like in the Samsung phones.
However, you are correct about wanting to pay it in monthly payments or like in my case to use Jump ON Demand with it, so what I did was to get it via Tmobile when they became available at the stores, I exchanged my S7 for it (I kept my S7 edge) and after a couple of days and realizing the updates on Tmobile will be a nightmare after seeing that even to buy it I needed to ask for it as it wasn't even on display (so far I was totally right), I decided to do the Unlock bootloader and S-off and changed the CID to the Unlocked US version and installed it's firmware. I saved my Tmobile firmware partitions so until there is a RUU for Tmobile I think I can go back with them if I need to.
So, right now I have a Tmobile's carrier version, that it's just like the US unlocked one, with the Unlocked version and getting all the updates as soon as they are available whole I'm paying the phone monthly and even better, if I get tired of it later I can put back the Tmobile version (hoping that it appears somewhere at some point), lock the bootloader, do the S-on and go to Tmobile and do another change for another phone under the Jump ON Demand program. Best of both worlds.