I'm still learning the Hill Start on my used 2016 bike I bought earlier this year but so far this is what I've figured out. The bike needs to be at a complete stand still, pull the front brake lever all the way kind of squeezing it hard, see that the H shows on the dash when it's set.
To release it you can either just start moving by twisting the throttle normally but there will be a hard spot while first twisting it before the bike actually starts to move
The other way is to pull the front brake lever a second time and the H will disappear and the brakes will be released.
Again I think the main thing is that the bike is at a complete stop and the wheels aren't moving at all before the H will appear when pulling on the front brake lever.
I agree with all the above, on my 2018 B I have also noticed that the abs warning light flashes for a moment as you drive away without releasing the hill start first and that if you kill the engine while you have hill start engaged it releases the brake
however I think it is a really useful feature especially as I have got used to it on my last few cars.