Adherents of yoga spend a lot of time on their heads or upside down without the use of boards. Perhaps that’s where the manufacturer got the idea? I would suggest that a good yoga school would be of greater long term benefit as well as having the potential to be socially quite liberating.
In addition, much yoga is performed with music. Beethoven said that music is a higher revelation than all wisdom or philosophy. Beethoven was right. The CIA famously don’t play music when water boarding.
By the way, I ought to declare that I have no medical training at all, nor do I like standing on my head. I do however adore Mozart’s music which is brain food and soul soothing too.