*DISCLAIMER* This is not speculation on what actually happened. This is just a contribution to the conversation.
In the crash video, if he was actually lower, it may have been an attempt to make up some lost energy. We don't get to see the previous figure, so it's hard to tell.
They are required to know every entry and exit altitude for every maneuver. Lets say, the plan was to roll at 250 and after the last figure they came out slow. Altitude could be used to gain some airspeed back.... Everything happens so fast. In the Stearman altitude costs airspeed and airspeed costs altitude.
I would figure it would be standard to know all entry/exit parameters for any maneuver; no different than any acro maneuver at all. My question as it relates to the maneuver itself is, is/was there a standard set of parameters for that maneuver? Or not for the altitude part of it (if it was indeed flown at a different altitude)? And if there was, and if the maneuver was performed differently or lower from before, was that some kind of formal change made, or an ad hoc one?