as i understand it, if there is an unexplained discrepancy you have two options.
1. continue with the LLZ app
2. conduct a missed app.
You can't continue with the LLZ approach.
Think about the
reason behind the rule. If you have an
unexplained error at the check altitude (so we are not talking about temperature corrections) then you MUST suspect your altimeter is mis-set (or has a large error). You thus would be pretty stupid to continue to descend IFR to ANY minima (such as a LLZ minima) knowing that your altimeter is mis-set.
The AIP rule is there to get you to go-around, identify and fix the problem (confirm the QNH, inquire as to the serviceability of the Glide Slope, inquire as to whether an aircraft was taxiing past - ie. it wasn't protected, cross-check altimeter/static sources etc etc) - and once it is fixed, you may attempt another approach (of whatever type).