Thread a couple of years old but i came across it whilst searching for ignition timing and what controls it on my 54 picanto.I think you are misinterpreting the readout. It is not showing advance from TDC, it is showing difference from the base advance. That 2 after is not 2 after TDC, it is 2 after the nominal firing point, which will be some degree of advance. Put another way the indicated 0 is already somewhere between 15 and 25 BTDC and your readout is showing difference from that reference. I doubt it would run at all if it were firing 2 after TDC at idle. WRT knock sensor - you don't expect knock sensing to be performed all the time do you? The only variable that the knock sensor is compensating is the quality of the fuel - this is most easily detected at idle and would be damaging if your engine was knocking at speed under load. The knock sensor sets advance parameter to get best out of fuelat idle and with that base figure the map can take care of the rest of the rpm and load range. Fuel does not change its characteristic except when you put more in so no need to continuously sense knock.
Do you honestly believe that you know the correct ignition timing better than the engine designers?
Tell you what - go right ahead and slot the sensors and report back here the results.