Happy reading....
https://developer.tizen.org/downloads/tizen-sdk
Ofc it can utilise c/c++, but compared to native toolkits like Qt/EFL etc, the entire HTML5 "API" (for want of a better word) is limited in terms of how deeply/broadly it hooks into low lvl libraries.
That's been gradually improving over time, but it's a slow process, & it's still some way off reaching parity (if it ever does).
This has all been discussed in great depth at TMO before, & you were around at the time...

EDIT: looks like they may in-fact still be using a native library alongside HTML5, not sure what it is exactly, I know they did sideline EFL