I need quite many 0-15V voltage input so AV-inputs are full. I planned to use AT-inputs for rest because manual says it can handle 0-15V (no need for super precise), but there is pull-up resistor to 5V so that would mean it would backfeed input voltage to 5V supply. Yes, I tested it
and it will make display crazy 
Analogue Temp Inputs
Measure Voltage Range: 0 to 15.0 V
Note: Voltages outside this range may affect the
readings on other inputs.
Input Resistance: 1000 ohms pull-up to 5 V sensor supply
+100 k to 0 V
Is there something I don't understand, or why manual says you can if you can't?