Part of it is that both of his parent (and both of ZT’s parents have the non-curly gene. The curly gene makes coats MUCH harder to maintain and many breeders don’t test for it, or if they do, are just careful not to breed two carriers together so they don’t end up with Poodle-like coats. But even a single curly gene can make coats difficult. But there is more to it than we can test for genetically, unfortunately. Some lines have more frizzy, thick undercoats that just mat more. Ducky has a lot of undercoat, and ZT has MASSES of undercoat. But in both of them, it is still silky soft and not prone to matting. Most will STILL mat through the “dreaded coat blowing”… I was REALLY lucky, and Ducky didn’t even mat much then.
Also, NO Havanese should need to be “shaved” unless their owner allows them to get BADLY matted. Even a Havanese with a Poodle coat can be kept in a short puppy cut and look adorable. But people need to get them groomed BEFORE they mat, and new Havanese owners are often not aware of the matting, and do not comb them down to the skin. They do not understand how to groom a coated dog And don’t keep on top of it.