Yes, definitely allow the system check to complete, before allowing it to start. LR should really have added a delay to the start to avoid starting while the check was being carried out, just a Ford did on the Kuga, but alas LR didn't.
The extra cable was introduced on the production line around 2010, later cars having it from the factory.
There's even a position on the negative battery terminal to attach an extra earth cable, you simply need an M6 bolt to do so.
It's easy enough to do DIY, you need a 75cm or so battery cable, with an M6 ring on one end, and an M10 on the other.
This cable is the connected to the upper starter bolt (10mm lug), routing it backwards with the main engine harness, over the gearbox and up to the battery box, so it can connect with the battery negative terminal, where the 6mm lug is joined to the spare M6 thread, using an M6 bolt.
It's a quick and easy mod, which helps prevent various issues when starting.