Single-wire spades from amp to biwire spkr posts?

All the major cables provide and internal bi-wire option which is what you're asking for. No problem.

Almost all bi wire cables come the way you speak. If both end had 4 wires, it would be for bi amping in most respects.

Thank you for that. I will do some more research.
From the photos I looked at on some major cable websites,
I only saw biwired cables with 4-wires on each end of each cable. I didn't see an internal biwire option,
or any distinction between bi-amping and bi-wiring.

I just hate stacking spaded-connections on one post.
When I did that once for jumpers, they would occasionally
detach themselves.

It's also possible to have externally bi-wired cables, two lengths of cable going to each speaker, with the two cables joined at one end so that you have only one set of spade terminals at the amp. I've owned Dh Labs and Silverline cables configured that way.