This page (which is the first hit reported by a Google search on >maze bright<) makes clear that the phrase means approximately ‘capable of figuring by yourself out what you need to know and do in a new job, without formal training’:
Unless everyone is 100% Maze-Bright walking in the door and will come up-to-speed quickly on all the intricacies of stakeholder requirements, products and services, processes, organizational and job roles and responsibilities, and strategic changes needed, etc. – you might consider providing some guidance.
The author (a training consultant who has been in the field since the end of the 1970s) says he “first heard of the quality of being “maze-bright” in the early 1980s. It was an incoming requirement in most of the big Fortune 500-type organizations that I worked in.” I think it very likely that you are correct in deriving the phrase from psychological tests measuring rats' ability to find food in a maze. The earliest use of the phrase I have found is a study by W.T. Heron and B.F. Skinner, "“The rate of extinction in maze-bright and maze-dull rats”, Psychological Record, 1940, 4, 11-18.