You’ll get many different opinions on this. Yes, it is true that some manufacturers don’t believe in biwiring. Although Harbeth does not believe in biwring, they have provided biwiring terminals on most of their speakers to satisfy market demands. Chord Cable has dropped all their biwiring speaker cables as they maintain their stand that a single run produces better results than biwired cables.
The other good reason speaker manufacturers provide biwiring terminals other than following the "trend" is to give users the flexibility of biamping with a pair of amplifiers. That will only useful if the loudspeakers are demanding.
Coming back to the question of aftermarket bi-wire links. You may try some but personally I wouldn’t bother. The difference in sound quality would be minimal even if there is a difference. However, there is no harm trying if you have some money to spend.
The other good reason speaker manufacturers provide biwiring terminals other than following the "trend" is to give users the flexibility of biamping with a pair of amplifiers. That will only useful if the loudspeakers are demanding.
Coming back to the question of aftermarket bi-wire links. You may try some but personally I wouldn’t bother. The difference in sound quality would be minimal even if there is a difference. However, there is no harm trying if you have some money to spend.