I compared the labs to a lot of other dogs from a variety of breeds – I didn’t do one on one breed comparisons with any other breeds besides German Shepherds (it’s hard to find any other breeds with enough dogs to do that!). So what this suggests is that labs have a personality profile – particular answers that are more likely for them than for purebred dogs in general. I expect the same to be true for other breeds (just, different answers).
So I don’t think it’s that labs are less behaviorally diverse than other breeds (although I haven’t tested that). They are still very behaviorally diverse! But as a breed they are more likely to like water and retrieving and meeting new people than other breeds (as a whole) are.
I hope that helps – let me know if not!