I just played the challenge on normal speed - hard difficulty and it plays out exactly the same. I got 80k on the first try with the same strat that I did on slow speed. So again I didn't cheese with tons of walls to make the AI run into the castle like most other people seem to do. I just wasn't quite able to take out orange completely since I was a bit slower with everything, wasted more units and didn't have the perfect eco setup due to not playing on slow speed. Not sure if 100k is possible on normal speed. Maybe for a player with better speed and multitasking.
I noticed that you can change the difficulty of the scenario by changing the difficulty in "Historical Battles". Did you try the same strategy on Standard before? The AI seems to act differently on standard settings, e. g. teal using its trebs to defend your push and maybe other things. Would be interesting how it plays out.