If you ask my why and then go on about how you dont want excuses, the convo is over.

A reason is an explanation although not all explanations are reasonable.

An excuse is an attempt to justify a reason/explanation.

Excuses are used when the expiation is not reasonable.

I think this person asking you is really trying to tell you you did something the wrong way, but in a less direct manner, because directness is considered "rude" in some cultures.

More often than not it's more appropriate to say "I misunderstood, how should it have been done?" or "Sorry, I wasn't paying attention. I'll be more careful" which may or may not include an apology depending on whether you inconvenienced someone else.

A reason is a motivation to do a thing. An excuse is a reason to do the wrong thing (though not necessarily an inherently wrong thing - just anything that the other person thinks was wrong).

excuses lend themselves to lengthy explanations. reasons are more succinct and pertinent

I really dislike rhetorical questions.

(got put in wrong place. Edited and put in correct place for proper response)