I'd argue that it is the most important time to be doing checking of this nature.
Here are the counts. They are based on my install which has a few extra nonstandard rooms in it.
Symbol Freq Type
1 # 260 1x1 Local Guard
2 $ 138 3x3 Local AOE
3 % 219 1x1 Jumpscare
4 ~ 76 3x3 Sniper
5 1 626 1x1 Pursuer
6 3 221 3x3 Wander
7 5 42 5x5 Wanderer
8 7 25 7x7 Fearsome
9 A 125 3x3 Attacker
10 d 30 1x1 Deadly Pursuer
11 h 85 3x3 Chaos-Adder
12 k 35 5x5 Chaos-Adder
13 L 28 5x5 Attacker