I’m wondering if the opposite might be true as well - underdiagnosing people from different months. I was born in March and in Poland where I grew up school was

I’m wondering if the opposite might be true as well - underdiagnosing people from different months. I was born in March and in Poland where I grew up school was assigned by birth year. So the oldest kids in a given class were from January, the youngest from December. I have had little problems in primary school and gymnasium without putting much work into it. Then in high school it got harder, but I still passed, again, without almost any work, skipping classes, being late all the time. I started really struggling at an university and later in life and I eventually got diagnosed. Granted, ADHD disgnosis was rather uncommon in Poland in the 90s, but I can see how a kid doing good early in school could have been not diagnosed.