With a grain of salt. Each of my Focal 806 speakers only has one set of speakers terminals so classic biwiring is not possible; however, I run four cables from my Marantz receiver terminals to each speaker, i.e., two for (+) two for the (-). A modified biwiring if you will. I notice by doubling the cable connections that there are: 1) More gut punch in the upper bass; 2) Palpable increase in "air" and crispness in the upper midrange where I can feel a slightly charged atmosphere similar to just before a lightning strike; and 3) The resultant sound is more tube-like without the ricotta cheese like grain of SS. Or I could be full of it.
Compared to what? If you KNOW that you are using these "buy wire" cables, then you can hear the difference. The difference was already there before you fired the system up, in your mind. If someone else were to swap those wires out without you seeing them (assuming a cable that is appropriately sized for the speaker load), I would say with fair certainty, you would not hear that difference. Two sets of wires effectively increases the AWG of the wire, but the speaker still only draws the same amount of current.
The reason your speaker has one set of posts is because Focal didn't need them to market these speakers.
I do something similar to what you are doing as well. I bought bulk Canare 4S11, which is a single jacket 4 conductor cable, brining the price down significantly. I terminate both wires into one set of plugs, effectively increasing the AWG. Once those wires are combined into a single connector though, the "magic" of two wires disappears. I do it because I like the heavy duty jacket and it is easy to manage. I cannot say that I have heard any more air than my previous wires which were 10 AWG (8ft runs).