ok not being at all argumentative but just saying any horse who sees a smaller option is going to take it. If I saw an easier way out of doing something id be the 1st to take it!
*Butting in here, but this statement is absolutely bonkers, and it dismisses the arousal of the concept that he is uncomfortable
jumping the height you are pushing him for.
Very lovely horse to be so patient for you. Just work on a lot of small grids and such.
Although height is fun, it is easy to ruin a horse by pushing them to far ultimately resulting in them having an uncurable fear of jumping all together. So just be patient, careful, and take your height advances SLOW.