Hypothesis: Aziraphale under his highest level of stress just simply makes no sense. The most dissected lines of the series are all things that Aziraphale says when under extreme stress and they just kinda don't make sense, which is why we've spent so many fan-hours trying to make sense of them.
Follow me, if you will, on a journey:
Aziraphale, discorporated, having defied Heaven for the first time in 6,000+ years, and in search of a body to possess, demon-style, hears Crowley sob, "I lost my best friend," referring to him:
"So sorry to hear it."
Aziraphale, having just given the love of his existence the means to destroy himself completely, at great personal risk to Aziraphale, is offered a ride, "anywhere you want to go," while barely managing to stave of a full-blown human panic attack:
"You go too fast for me, Crowley."
Side dishes:
Aziraphale, having just discovered the infamous Nice and Accurate Prophecies of Agnes Nutter, Witch, in his lover's backseat, days before the apocalypse, and clearly in a state:
"Tickety-boo! Mind how you go!"
Aziraphale, having broken up with and completely disavowed his demon lover in a dramatic public display days before the apocalypse, sees said estranged demon pull up at his curb and shout desperate apologies in front of everyone and God, then insult his intelligence:
"I forgive you."
We know that stress and trauma affect cognitive functioning and the ability to verbalize. I know Aziraphale is an ethereal being and technically doesn't have a human nervous system, but I think it is part of what's so amazing about Neil Gaiman and Terry Pratchett's writing, is that sometimes, just as in reality, dialogue doesn't make sense. Just like the whole story, the whole point of the series, it's up for interpretation. Even Aziraphale might not know what he means, or even remember saying it later. That's how trauma works sometimes.