Nope. Much simpler. Just enabling the use of the other data lanes that were already in the cable waiting to be used one day.
USB-C has 4 differential twisted pair data lines.
USB-C has 4 differential twisted pair data lines.
USB 2 has a single twisted wire pair, specced for moderate speed.
USB 3 replaces that with two pairs with much tighter requirements, one for transmit and one for receive. This involves a tenfold speed boost (.5Gbps to 5Gbps), with much more modern transceivers using much higher frequencies on much better wires. But it also drops the length a single passive cable can be from about 5 to 2 meters.
USB C doubled the number of pins while making the plug reversible, so they went ahead and made the special case of C-to-C cables connect to all the pins and have four pairs of wires.
But that's only a doubling from 5Gbps to 10Gbps. How are we getting up to 20 or 40? It's mostly coming from restricting cable length even further, down to 1 meter or only half a meter. But on the bright side you can get an active cable, with chips inside, that can get you back up to 1 meter or 2 meters or 60 meters. As long as you're willing to pay enough.
I have a couple of situations I would like a 7m-ish Thunderbolt 3 cable but can’t seem to find one, even for the multiple-hundreds it would probably cost.
It's really disappointing that Display Stream Compression hasn't been built into everything for the last 5+ years, and is only now barely getting into equipment. 2:1 or 3:1 compressed display data looks fine, and being able to add more pixels or bit depth or refresh rate far more than makes up for the tiny losses. Without it, tons of screens are stuck at significantly reduced framerates or 4:2:0 subsampling.