Does length matter ?

doesn't matter that much but ocd prevails usually

Keeping the same length is the “correct” thing to do. I have just always stuck with the rule. Once I had heard the huge differences in interconnects and cables... and had gone through extensive (hundreds of hours of) comparisons carefully noting the differences that they made on components, and found sonic differences in stable platforms... I just dicided it was easier to go with the conventional wisdom instead of testing and proving it to myself. After all, it is just a yes or no question. Just safer to keep them the same length. I have read professional reviewers say why it is important.

Of course you should if you can.
By connecting speakers to an amp you are creating (or extending) a circuit and, since in stereo we have two channels, i.e. two electronically identical circuits, it's good to keep them that way. By using wires of different lengths, the circuits are dissimilar.
The sonic effects are, of course, minimal in most cases

There's no technical reason to keep them the same length (within reason). That cable is 1.03Ω/1000ft, so if you had one 10ft and the other 20 then the difference in resistance would be 0.0103Ω which is negligible and will make no difference to the sound quality. If one is longer than it needs to be then you may inadvertently create an inductor where it coils back on itself, this is also unlikely to impact audio unless there are a fair few turns.
If you are worried about the time difference between the cables, for the 20 and 10 ft example it would be around 10 nanoseconds or 1 cycle at 100MHz... which is again negligible in audio.
I suggest the best thing to do is to cut each cable the length it needs to be to reach from the amp to the speaker.