I disagree that this is a case of inverse error, Top Dog. Obvious cyberlimbs "may" be bulkier than normal limbs, but that doesn't necessarily mean that they automatically stand out, either. Case in point, the limbs cannot be customized (in terms of stats) beyond the frame they are fitted to.
As such, unless there is a large discrepancy between the characters body, strength, and agility attributes and those of the limbs, I do not believe there is any cause to require a palming test; how would you conceal your own arms, after all?
As you say, the rules do not provide for this situation, so the only guidance we have is "they are immediately recognizable unless covered with clothing". You may call it a logical fallacy if you wish, but in terms of rules that's all we've got, so I'll choose to interpret that as "you can hide obvious cyberlimbs under clothing if you want/need to".