Lego blocks have been the simulation selection of choice by many trainers because they are readily available, inexpensive (if you don't consider the Escalade needed to cart them around) and they do a quick job getting the basics of the lean flow across. So what do they miss?
Anyone who has spent any actual time in the shop with hands-on assembly of product knows that not all parts are created equal (except Legos) and that the randomness and variation in the components fit and finish present a challenge to the idealistic flow.
The LeanMan simulation products are designed to provide some natural size variation like the wooden pegs, or finger-fighters like the small stackable metal parts; plus some intentional variation for measuring the effects of non conformance on quality like inserting the black wheels into the flow. The resultant metrics are realistic, repeatable from team to team, and add an element of finesse to the event missed by the overly simplistic Legos or by trainers who have never worked with their hands in a shop.