The Centre hydraulic isolation system designed in 777 sort of isolates the leak in the lines with help of 2 isolation valves (for proper nomenclature refer AMM HYD chap - CHIS)
unless the leak is below the standpipe levels I think CHIS is quite useful.
I think it would be wiser to stick to the ECL and let the underlying design feature takeover and sort the issue.
you might have managed to extract more from the a/c with such a leak than what it intended by switching off CTR HYD pumps and saving your fluid.
While many things are undisclosed in 777 I would always suggest to be fully aware of your smarter options but exercise them wisely espcially when it's out of the book only when there are very compelling reasons.