Yes, manufacturers often bundle 2 smaller cables to share the amperage load than 1 much thicker and stiffer cable. Most likely the maximum amperage of the smaller cables is exactly half the amount needed.
Unless the cables on the inverter are exactly what you need, they often are substandard cables, and you are better off choosing properly sized cable for your uses.
My Victron Multiplus supports two DC cables for each positive and negative connection. I made use of those connections. Minimal voltage drop in my system.
I think you missed what most people are saying. Even using both of the supplied wires for each connection will leave you with insufficient wiring. Throw away the supplied junk wires and use proper wiring.
Tell us the size of the inverter in watts and your system voltage if you need help determining the correct wire size you should use.