When Hive Blockchain was launched all existing Steemit accounts of that time were also created automatically on Hive. They show all activity of Steemit on Hive upto the day Hive was created. But from that point onwards both accounts are separate. Content posted on one blockchain doesn't appear on the other.

I am not sure though why your account is created there because apparently you joined Steemit later in 2021 and Hive was launched in 2020.