Concur to a degree, but there may well be truth in the (oft peddled - rarely backed up) line that it diverted OCA assets to a DCA role on the main land.
This would be easy to quantify if we knew which units were reassigned to protect the main land vice sweep the Falkland Islands, where they were reassigned from, how much they flew and what they protected.
There may be other reasons for OCA being limited over the Falklands (other than distance and no AAR for Mirage and Dagger) but I'd like to know what they were - not just surmise what they might have been.
For example: It is plausible that the Argentinians didn't lengthen the runway at Stanley because they had no tractors and diggers, because they didn't use sea lift, because of the SSN threat - nothing to do with Blackbuck...but that would just be a uninformed guess. It might be that Blackbuck was the reason. But without talking to the Argentine airfield manager it's hard to find out.