One of our Shia brothers used to do taqleed of Ayatollah Khoi. After his death, he was told to follow his rules, but in new issues he did rujoo to Ayatollah Sistani. But recently, somebody told him that Ayatollah Sistani allows a muqalid to follow him in all the rules and not just new issues. Wanted to confirm if this is true?

He has the choice to stay as he is, or to fully follow S. Sistani