Not so sure about skills courses, but apart from confidence boosting, what exactly do you learn ??? Aidan above says cornering, but thats body position, weighting etc. with practise that just comes ( doesn’t it ? ) For a novice being shown the basics could help, but everyones a bit different, there’s not one perfect style that makes everyone better. Look at the pro’s hardly any ride exactly the same. At the end of the day your riding will be limeted to your physical abiliities, balance , coordination, strenght and stamina.
What goes on during a days training to improve those attributes ?? I could go on a 100 training courses on how to slam dunk a basketball, but I could never do it.
Practise will make you better, not so sure about the psycological placebo of a days skills course.