I usually avoid this discussion, but...
I like those two 10 gauge wires hooked up with the 4 gauge wire. It looks cleaner. You don't have unprofessional taped up hot ends hiding in your harness. Those wires are hot, hooked up or not. The same fusible link has the same power going through it, hook up or not.
The fire hazard comes from those overloaded factory 10 gauge wires heating up, melting the 2G power connector, then blowing the fusible link (potential fire). The added 4 gauge wire relieves the circuit from overheating and there's no 2g connector to melt.
The only real threat of leaving the 10g wires hooked up, is if the 4 gauge wire fuse blew, leaving the fuse link there to protect the circuit alone. But that's unlikely, because the 4 gauge wire circuit protection is such that the event of a dead ground, the fusible link would go first.
Your car with a 3G hooked up with or without the factory 10g charge wires, is sooooooo much safer as far as fires, than the stock 2G alternator was with that 10g wire alone.
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