Personally, I like to interpret it as "Paul's portrayal changes as Ash's view changes." The show is mainly told through Ash's POV, which before DP had never conditioned him to believe in anything other than the usual "friendship conquers all" mantra. Paul gets written as a straightforward nasty douche because Ash isn't capable of seeing him in any other light. But as the series goes on, Ash's respect slowly grows, and the show's portrayal changes to reflect that.
I just interpret it as: Tomioka liked Paul too much and wanted to force me to like him too, so he retconned his character in order to make Paul look better.
I didn't fall for this trap.