That's rather meaningless number intending maybe to shock some folks who don't understand math/physics etc for many reasons, just randomly: atmosphere takes a bit out; we will never be 100% effective (but 50% is not unreasonable); we can't cover even 1% of earth surface with solar panels even when ignoring most are oceans, that would be absolutely massive use producing staggering waste and due to curvature of Earth only a fraction of them would be useful at a given time.

So what you are basically saying we have to support solar with other sources, always, by principle. Still good supplementary stuff unless you are too north/south from cca equator, there it will never be a major thing.