Most people probably don't realise this, but this forum has had two editors for a number of years. One is the xenForo default editor, and the other is a custom editor I made years back I called BBCEd.
All the settings for which editor you use was lost during the upgrade. You can find the setting under Account Settings > Preferences > Editor.
Say for instance you have CD CD 41 00 as byte code. CD is interpreted as the "CALL" instruction, which has a two-byte argument for a total of 3 bytes.
If we execute from the first byte we have:
CALL $41cd
NOP
However if we execute from the second byte we have:
CALL $0041
The two couldn't be more different, and without the context of the other instructions either possibility is valid. So you would have to traverse all executable bytecode for each NPC. It is impossible to just parse just one instruction without a wealth of false positives. Not to mention you can't even know where all the code is located without parsing jumps, plus, as Enlightened said, there is no guarantee that the instruction in question is setting framerects.
If you want accurate detection of framerects then you need a virtual machine. Have I said before how absurd a notion that is? Because it is.