USB cables push the boundaries of signal integrity hard enough that unless it's a 1 foot passive cable you're not really going to get any surprise speed boosts.

And when they upped the max voltage they didn't do it for preexisting cables, no matter what the design was.

> those features depend on compatibility from both sides of the plug

That's easy to understand. Cable supports (or doesn't support) device, it can't give new abilities to the device. It doesn't make labeling less valuable.