Would learning to ride a unicycle boost biking skills?
Here's my contribution: There is one bicycling skill that improved a lot after I learned unicycling: Riding the bicycle with no hands. 
Before unicycling I could ride the bike with no hands in a straight line and do wide turns.
After unicycling I was a lot more confident to go over obstacles and do narrow turns.

Now when riding some long distance biking, I often leave the handlebar for a while to straighten by back and relax. Even in uneven or difficult tracks. 

Apart form that, it contributes to your leg strength and general balance.