The midnight exercising thing was in the real wild west days of the early-mid 90s, the reason the teams brought it in house was to prevent those kinds of scenarios and ensure it took place at least under some kind of medical supervision. Unfortunately, how good that supervision was depended on who your doctor was... Fuentes at Kelme was routinely dosing riders with all sorts.
Oh for sure, but it was seldom one of those things people did on the spur of the moment. It was very heavily calculated and planned.