BG-E11 grip - battery management

This question is for the Canon BG-E11 grip and how it manages its battery usage. My 7D battery grip effectively alternated between batteries when I wa shooting, keeping avery close shutter count between the 2 batteries.

I know the 5D3 frame rate drops as battery voltage drops (per manual and per experience) but I am seeing a very unequal usage of the batteries in my grip. it appears the battery in position 1 gets the usage entirely until some future point ( not yet observed what charge value results in the switch) at which time battery 2 will be used.

has anyone observed such an unequal distribution of battery usage in their Canon BG-E11 grips? If this is a design feature I would like hearing. Otherwise perhaps my grip is defective and I need to swap it out while I still can! Thx!
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Please forgive the typos! A great speller I am, a great typist I am not!

I have shot with both Nikon D800 and Canon 5D3