IRCC has 3rd party agencies in other countries who do this BG check work for them - clearly they haven’t responded. Till the time these third party agencies dont give clearance, IRCC obv will keep file open. The ball isn’t in their court and that’s why no timeframe.
These agencies work with govt. of that country to retrieve info so in short it’s a govt. clearance (somewhat like PCC), and they decide who gets faster or slower clearance.
I heard a minister say this during recent discussions/ tensions brewing between India-Canada.