While I do not, nor have I ever play tested for FFG or AMG, I did do a lot for another company that is no longer around. We went in to their offices every saturday and chose one of the games in dev and played several hours using latest set of changes and reported back results and thought as well as suggestions. Sometimes thing went really well, other times... let's just say we got to see something very different the next week. We were not allowed to disclose what we were doing at that time and you had to be invited in by one of the chosen few. After 8 hours of solid testing, we would take a dinner break then come back for a HUGE mini game. Era and scale always differed but the game table was about 4'x30' with rough 8-10 people per side. The game might have been one of their in dev or just something everyone wanted to play. Full terrain and hundreds or thousands of minis depending on the actual game. Miss those days. Pretty certain most other companies have something similar in their offices. Last note, not everything we worked on made it to production. Somethings were just inherently broken while others just did not really do anything to add to the game and they got scrapped. A few thongs were designed to only be a testing product so special rules could be better tested, think SUPER ssd. Silly and absurd but allowed for finding odd edge case rule issues. Not directly related to the op questions but general insight into the industry.