https://www.reddit.com/r/apple/comments/5d7xs3/2016_15_macbook_pro_i7_29ghz_pro_460_512gb/Link to the temperature test when dGPU is used for both models? 35W vs 50W doesn't translate to external temperature on the body of the laptop. Maybe the thinner body makes heat dissipation worse.
Scroll down to the "Notes" section. Max temp hit 72 degrees celsius
https://forums.macrumors.com/threads/macbook-pro-15-mid-2015-temps.1934472/
This person had his 2015 model going up to 99 degrees celsius