I dont think you get Different Treatment.

I was flying on a FULL FARE - J from FRA - YYZ seated in the last row (11A). and for some reason it was a full flight and i know some people got upgraded because they were first seated in ECO and moved before boarding with a new seat.

When the FA was taking orders for lunch, there were 2 appetizers being offered and when i asked for the one i like, the FA said sorry were all out of that so i ended up getting whatever is available.

I noticed one of the person sitting near me who got upgraded have the appetizer i want. so i think this shows that Upgrade or FULL FARE dont make a difference.

by the way im just an Elite. but with a full price fare!