Dog Coats

Yeah, it's one of the reasons doodles can be significantly harder to maintain than poodles - they can absolutely get a double coat, and if the undercoat sheds a lot into a non-shedding top coat where they get trapped, it's a huge nightmare. Just mats everywhere all the time. Poodle people tend to dread 'coat change', when a puppy starts growing in adult fur and sheds their puppy coat more heavily than they ever will again. Causes a lot of the same thing - tons of dead, loose hair caught in the healthy new coat, constant brushing - it's so bad that if you're not going to show the puppy, most people just shave them down over that period. With a doodle with the fur/hair combo, you're basically stuck in that stage for the life of the dog.

I actually get a taste of the double-curly-coat problem having a Lagotto - they have double coats, but both are curly, hair-type fur. It's why the breed tends to 'felt' like sheep rather than mat to the skin, and many working Lagotti are left that way and the only 'grooming' they get is a shave down once or twice a year. Since Frodo's not a working dog, I do a lot more brushing, combing, and trimming and boy howdy is he a different beast to maintain than Sam's single curly coat. To be fair, Samwise also has one of the worst coats I've ever seen on a poodle - limp, soft, almost wavy instead of curly in places, and gets soaked to the skin in seconds instead of being a tight, crisp, springy waterproof layer - so it's hard to compare his coat and its requirements to even a well bred poodle, let alone a different breed like the Lagotto.

@Beta Man Well yes, both fur and hair are chemically the same. However, when talking about hair vs. fur on dogs, people are referring to the growth cycle. Fur goes through the natural growth cycle of a follicle very quickly, and has a short anagen phase, where the hair is actively growing. This means that 'fur' follicles shed and regrow much more actively. When we say 'hair', we mean a type of follicle that has a much longer anagen phase, much like human hair does, and only sheds a (relatively) few hairs at a time. What we're talking about here are dogs who have an undercoat with a short anagen phase combined with a topcoat with a long anagen phase - especially if the topcoat is wavy or curly (as opposed to silky, like an afghan), since that texture catches any dead hair/fur more easily.

There are some variations, such as the Samoyed coat, which spends a relatively long time in the telegen or 'resting' phase, and therefore explains why they have a 'fur' coat but still shed pretty minimally outside of the seasonal coat blowing. But since it still has a short anagen phase, it's more like fur in its appearance and care.

Lots of people do use fur and hair interchangeably, but when it comes to a discussion specifically about coat types, there's definitely more precise differences between the two.