Why do you think Bi-Wiring improves the sound ?

Simple answer on question on if bi-wiring improves or not sound is - yes, it will improve sound.

The longer cable is, the better improvement will be. Alternative to bi-wiring solution to improve sound could be mono-blocks closer to speakers, and shortening cables. If speaker cable is 2ft or less, bi-wiring will not improve anything much.

Main reason to have bi-wiring option is a fact as speaker is not linearly behaving load, and therefore sharing cable connection resistance and inductance will increase intermodulation between low/mid/high. For low freq. speaker resistance of cable should be lower than mid/high, because speakers (almost) never use crossovers with additional in series resistor for lows, and also utilize lowest ESR Inductors $$. Mid/High  crossovers typically have couple of Ohms in series resistors, and therefore 100 mOhm cable resistance does not make any difference. The most important for Mid/High cable is to have lowest as possible inductance. 

mahgister wrote: "In my experience bi-wiring never improves the sound”

more details needed to understand findings: 1) speaker: impedance/ 2Way or 3Way / speakers internal x-over design 2) length/resistance/inductance of cable 3) amplifier used

bi-wiring will “tangible” improve sound if: 1) initial cable is long (6+ft, high resistance 50+mOhm, high inductance 2) amplifier is high quality 3) speakers are 3 way

@ alexdv1: thanks for posting this link! I agree 100% on technical details for bi-wiring there. from schematics side, bi-wiring is a two independent networks connecting presumably low output impedance amp to lo/hi speakers, while single cable is shared cable impedance between lo/hi thus lesser speaker isolation https://www.qacoustics.co.uk/blog/2016/06/08/bi-wiring-speakers-exploration-benefits/