My dad fly's full scale aerobatics in advanced. It has alot to do about energy management but you have to compare the sequences that they are flying.
The Intermediate (IMAC) is almost the same as advanced (IAC).
The advanced (IMAC) is almost the same as unlimited (IAC).
The unlimited (IMAC) is way harder than the (IAC) unlimited.
(IAC- is the full scale aerobatic club.)

Some of the maneuvers would put too much strain on the pilot and the airplanes would stall and fall out of the maneuver.

They have made the sequences hard because almost everyone is flying a "overpowered" airplane.