To ground or not to ground a Lynx distributor

A Victron video describing the Lynx distributor, points out the grounding point to be used. This will couple DC negative to ground i.e the same as AC ground. The instructions for my battery a BMX ESS X (10Kw) spcifically states not to ground the battery. No explanation why. Any views?

It depends on of you have a fixed system or mobile.
And grounding is one of those grey areas…