It has to do with patterns.... do they have a history of doling out apologies but never really changing? This suggests insincerity in the apology. Now some people struggle with habits and have lapses, but I need to see genuine attempts to improve.
It has to do with how they apologize.... is it the blame shifting “I’m sorry you feel that way” pseudo apology or do they take responsibility for their part?
I actually prefer an explanation too. I know a lot of people think it’s making an excuse, because I’ve seen them take my explanations that way. I take it as a way to learn how someone’s actions may not have had bad motive or how it came from an innocent place and what it says about how they truly feel. The important thing is that they learn that whatever their motive, they now need to adjust to have a result in line with it. And I may actually adjust how I interpret their flaws, if that’s what led to an affront. I can’t ask for perfection, so it helps to understand a different perspective so I don’t take their weaknesses personally.
I do think that emotions often take time to subside and it can be unrealistic to expect someone to go from hurt to 100% okay in a matter of minutes. It can take time for the apology and new information to me processed and affect you accordingly. INFPs in particular may need alone time to process stuff fully.
That said, even with a shallow apology, I may offer shallow forgiveness. I will keep my eyes open from now on, if you know what I mean. A pattern in this way may make me distance myself from someone. I wouldn’t necessarily hold a bad feeling towards them, but they’re not someone I’d become close to.