I see what you are saying and broadly agree. However. It is stated in the series that a skilled telepath is able to focus and refine a subjects memories and take subjective memories and acertain the truth from them, to access the sub-concious as a recording device. Mind you its also clear in the series that a strong willed person/psion is able to resist and perhaps even deliberately mis-lead the telepathic reading deliberately...
I cant remember if I covered this in the Psionics sourcebook, but I know that I allowed for a non Psion to resist with an opposed presence/willpower check (plus one difficulty level)