I don't think it's that confusing - or may be I'm confused in not feeling confused! (I'll rely on [MENTION=6801328]Elfcrusher[/MENTION] to correct me if necessary.)
At the table, the GM tells the player to roll a save vs ZoT. If the save succeeds, the player is free to stick to his/her standard narration of the PC.
If the save fails, the rules of the game require the player to have his/her PC hand over the information to which s/he has access - in this case, that is the information available to someone with an INT of 5. Assuming that information is false or wildly incomplete information (because that's what tends to happen when you make an INT check with a -3 penalty), the player is obliged to have his/her PC hand over this information.
In the fiction, this is narrated as the PC's patron (or love, or . . .) having protected him/her from the truth-telling magic, and the PC instead repeating the deception/error mandated by his/her patron (or tiger, or . . .).
Whether or not this makes for a good game, I think the basic idea is fairly straightforward. As far as the adjudicaiton of ZoT is concerned, it prioritises mechancial effect over a strict in-fiction reading. But that's not surprise, because we've already gone there in entertaining this approach to INT narration at all.
Isn't that's what's happening here? The player's concept is of a PC who is poor at achieving his/her goals by way reasoning/mnemonic endeavours (because his/her judgement is clouded, or s/he acts at the dictates of an external agent, etc). And s/he builds that PC by giving his/her PC a low INT, which means s/he is unlikely to succeed at action declarations pertaining to reasoning/mnemonics.