I looked all over and RTFM and the pictures on the process were anything but clear on the location of the second plug to fully drain the cooling system at least to me. When I did locate what I thought it was I had a moment of consternation as it does not look anything like part of the cooling system and it is in a very strange location to access if you don't have the full underpan removed.
Here is what the manual shows. First image is the plug in the plastic radiator housing which is a bugger to get out. Second is the underbody or block location.
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The plug is a 17mm allen head and is in there tight! I had to use a 1/2 breaker bar to loosen it. It is much larger than the picture in the manual shows which is backwards from normal


Be ready once you pull it most of the fluid comes out from this plug and not the radiator at least in my case, and it runs everywhere because as it drains it hits the cross brace which makes a nice channel to dump everything on the opposite side of the car from where my catch pan was. Next time I will have a funnel underneath it instead of a catch pan. Needless to say make sure the car is very cooled off if doing this the 3 times JLR recommends when doing the flush procedure.
Put back in a little over 10 liters, but I have a larger intercooler. I would think 9.6L is expected amount of coolant required.
Which means if doing the complete flush and fill process you will need to test concentrations as the water in the system will not be completely removed in the case of adding back in a 50/50 mix. Another thought with aluminum components is you may want to flush with distilled water instead of the garden hose to eliminate and contaminates or harmful chemicals. Might be overthinking this part though.

I did not have access to the tools for a vacuum flush, so can't compare if it would remove the same amount of fluid, but if you can rent the tool it sure would be easier and cleaner I think.

This may be common knowledge but didn't see anything so thought I would pass along.