Better summary: The IDF is making efforts to get civilian out of a combat area. Hamas is trying to keep them there as human shields.
The ominous sounding "General's Plan" is to cut an enemy force from supplies. Which is a valid and legal military strategy, and one that's used in basically every war. Note the key part of the plan to move civilians from the area so it's only enemy forces that are cut off from supply.
And we really don't know if that strategy is even being employed. Israel nearly always warns civilians to leave areas where there are significant combat operations planned. Why would this particular warning indicate anything beyond that? There's a lot of civilians there, and there's Hamas there. All we know is that the IDF wants to attack Hamas in some way without there being civilians in the area.
So it's just a rumour the BBC is spreading in this article in an effort to appear "balanced". If they simply reported the facts that the IDF is trying to get civilians out of a combat area, it might sound like they're saying that the IDF is doing something good. Can't have that! Gotta put something in there for the ghouls that are still upset that the Gaza famine they were hoping for didn't actually happen.
Really it may not even be feasible to cut the enemy off from supply in an urban combat scenario. We really don't know how much food Hamas have stockpiled (while also pushing claims that Israel was trying to starve Palestinians). But it's understandable that a military might try to think of ways to accomplish this given the whole "cut the enemy off from supplies" is basically the default strategy in any military operation.