The reason that Mariott does not need to use the perfect form (having read) in her particular sentence is that the use of the word "after" makes it completely unnecessary. That is why I mentioned in my first post that using the perfect form would tend to sound "excessive".
It is completely natural and also perfectly grammatically correct to word her sente
Thank you, Yankee; I didn't know that. I makes sense, though. Especially when comparing it to 'After I had read the letter, I thought about it' and 'After I read the letter, I thought about it' it does. English is not my first language, so I'm just repeating what I learned in school.