We all draw our lines somewhere different, of course, but to my mind, taking into account Wardle's specific choices as exposed in the source code feels like cheating, vs taking the full list of 5 letter words that his code "accepts".
Knowing what answers are actually "true" ahead of time is more information than I'm comfortable taking advantage of.
And yes, eliminating letters is crucial - in my opinion it's always better to guess 5 totally new letters for the second word.
I don't know anything about the source code, so cannot be drawing conclusions from it. Preferring non-inflected words is just good policy, for somebody running such a game.
Knowing what answers are actually "true" ahead of time is more information than I'm comfortable taking advantage of.
And yes, eliminating letters is crucial - in my opinion it's always better to guess 5 totally new letters for the second word.