No it doesn't. It shows that Quirrel knows what to say in response to being accused of trying to kill someone to make it look like that wasn't actually his intention.

So him having an excuse prepared for when he casts AK and doesn't end up killing an Auror is evidence that he was intending to kill the Auror? Then him not having an excuse for when he fails to kill the Auror would have been evidence that he wasn't intending to kill the Auror..

That he had an excuse ought to be evidence that he was intending to cast the Avada Kedavra and miss. The story makes more sense that way, too: Consider what would have happened if Quirrell had actually killed the Auror, without some crazy reaction from Harry's magic. Now consider what would have happened if Quirrell had just barely missed. The first option has Quirrell and Harry in an emotional, full-blown argument in the middle of Azkaban with Bellatrix watching the Dark Lord berating a henchman for killing someone, and they haven't escaped yet. The second option has protestations from Harry quickly squashed and a ready escape, with Bellatrix seeing the Dark Lord mock his henchman for failing to kill, leaving behind an Auror who will tell everyone they are looking for a phenomenally powerful sallow-faced wizard all by himself, not a professor and a student.