i heard once in katha by giani thakur singh ji, it is mentioned in some old 18th century granth or book that in the times of bhai mani singh ji shaheed there used to be katha done daily in harminder sahib.
but i can not guarantee if it is true. only mahapursh who have darshan of guru maharaj can answer this kind of questions.
like baba harnam singh ji rampur khere wale asked few questions and giani thakur singh ji told sangat in the katha.