This is the data (charted) that they're using to make the claim:

Some methodology:

C-BARQ behaviour data for all 12 sub-scales were collected in March 2023 via an online questionnaire of owners of Cockapoo, Labradoodle, Cavapoo, Cocker Spaniel, Labrador Retriever, Cavalier King Charles Spaniel and Poodle dogs acquired aged ≤16 weeks from 1st January 2019. C-BARQ scores were analysed using multivariable linear modelling. Valid responses were received representing 9,402 dogs. From 72 behavioural comparisons overall

https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0342847