Yes Brad, I am familiar with painting the tree trunk with water based latex paint; in the past I used it on my Plumeria trees that had sunburn trunk. I also currently have Holiday avocado with such paint on it's exposed trunk; and that seems to help.
I just never suspected that this crack was caused by sunburn, but on second thought, I think it is probable. So, yes, tomorrow I'll find that light interior latex paint, put my dirty clothes on, and start painting the exposed tree trunks...
Thank you, Brad for pointing this, and sharing that YouTube link!