Angel saw Sherlock with a confident face, as if everything was under control. Initially, he thought he had met The Sage. However, Sherlock's reasoning was wrong from the start.
Still, this wasn't entirely Sherlock's fault.
After all, most of the Wizards of the Birlos Family went to The Garden Labyrinth ruins, a fact hidden from the public. The outside world was in chaos, and the reason why the Birlos Family had no large force to intercept was that they weren't in Bilun Tree Court at all.
Without knowing this, looking at the outside attacks again indeed feels shrouded in mist, misleading the reasoning process.
So, you can't blame Sherlock. It's just information asymmetry leading to completely wrong subsequent deductions.
But then again, whether it's Sherlock or the monk-garbed man, some of the reasoning is correct.
