On https://www.openstreetmap.org/way/350416529 the tag turn:lanes:forward=none;slight_right seems to be wrong. If you only can turn right, there is no need for 'none' in the same lane. Anyway, the lane seems to allow through traffic continuing onto road 65, so only tagging 'slight_right' seems to be wrong.   
If we fixed it to through;slight_right (as exists on the overhead sign, not on the road), the whole tag seems to be unneded, if it would just mark all the turns possible on the road (through and right), it would add no new information. There is no other possibility to turn, so why would we need to tag anything. But maybe there is something else you wanted to express with this tag. Please explain.