You are right. My issue is that there is no way of knowing what a USB-C/Thunderbolt cable actually does when holding it in your hands. And for the normal user, the whole situation is a complete mess.
Because I am aware of the issues, I only use USB-C cables of up to 2m (approx. 6ft) that are capable of doing everything Thunderbolt 3 is capable of and AliExpress stays out of my house.
And to follow-up to my dream in the post above: I just read a German IT article. A translated excerpt:
Because of the lower basis speeds of USB, it is clear that it is not necessarily downwards compatible to Thunderbolt 3. This is not the only difference in comparison to Thunderbolt 3. USB 4 is using USB-C plugs and can be used for hosts to put Display Port signals through USB-C, but the alternative throughput of PCIe packets is optional only. Apart from that, USB 4 uses a different topology in comparison to Thunderbolt 3. Thunderbolt 3 can be used daisy-chaining multiple devices whereas USB 4 still needs the known hub tree structure.
So, basically, it stays the same: even USB 4 land will not become Thunderbolt 3 land. They will remain compatible to some degree, but not in every way.
So, we will keep living in connection chaos to some degree, even with some more years down the road with a USB-C plug… Oh well…
So, the answer to “USB 4.0 is TB3” still is: NO!