It's not always about being too perfect, either. AI likes to squeeze all kinds of clauses or common sayings into one sentence which can make it sound lengthy and unnatural.

Sometimes the sentence structures from a native language comes through in English sentences, like you mentioned. When that happens and depending on the native language, the sentences can be lengthy and don't sound quite like someone more fluent in the language. The most common one that I've seen is when there is consistently more than 3-4 clauses in a sentence. That tends to trigger AI detectors.

For what it's worth, I didn't even notice English was not your native language from your writing!