It is a generational designation, with the F1 being the first labradoodle produced from a lab and standard poodle. The F3 is a third generation of labradoodle/labradoodle breeding. In my experience, the succeeding generations tend to be a little smaller (our F1 is 68 lbs and the F3 is 48 lbs) and tend more to the tighter curl coat.
Oh and yes, the F3 is definitely now much quicker than the 10 year old F1 😀
Here’s Bumper, a rescue dog nobody wanted. I think his last owners starved to death. He’s a bit of an old timer now, had him just over 15 years(he’s 17). By far the best dog I’ve ever had, does his own thing and pretends he’s never had any training.