The parent commenter is being naive. Of course you can make good guesses at which components fit where, and from there, which lines carry which signals. Most b

The parent commenter is being naive. Of course you can make good guesses at which components fit where, and from there, which lines carry which signals. Most boards in the plane are probably designed to have as little RF sensitivity as possible, and are also shielded. However, if you control the copper traces, you can definitely influence characteristics of the circuit. Presumably, those would be picked up in testing, because they are looking for those kinds of defects. But a semi-passive component underneath a trace, constructed to act a resistor/capacitor/inductor once every million pulses might not be.