If a BNT is Olympic quality and riding is full time training of horse and rider no.
If it is a clinic, possibly, if a BNT can be other than Olympic quality.
I have audited BNTs.
I have taken lessons and clinics with well known trainers and lesser known trainers.
I have 3 friends I can think of that sold or lost their fun in their safe horse and were then over-horsed by the trainer who wanted the ride on the better horse. Two of those three no longer ride and they were way better riders than I was. I lost track of the third. One of those who no longer rides was buying horses with 6 digit sales prices.
I am forever grateful for my trainers and my not so perfect to some trainers but oh so perfect to me horses who have had the patience of Job to work with me to improve my riding.