Completely false. According to the orders given Beauregard, "The delays and apparent vacillations of the Washington Government make it imperative that the further concession of courtesies such as have been accorded to Major Anderson and his command, in supplies from the city, must cease..."
The intent was to starve the garrison into surrender.
To decide on a tactic of starvation, then Beauregard would have to know the extent of the current food supply.
He did not. The “tactic” of starvation was contrived by Lincoln and the newspapers.