Thunderbolt 4 Is a superset of USB 4.
Not exactly.
As far as I can tell (and you have to read between the lines of a lot of marketing fluff) Thunderbolt 4
is USB4, except that a lot of the features that are
optional on a USB4-branded port are
required for Thunderbolt 4 certification.
E.g. the USB4 standard
can support 40 Gbps data (based on Intels now open TB3 tech) but it's an optional part of the spec, so your shiny new computer could have a port labelled "USB4 port" but not actually support anything faster than USB 3.1. If it's TB4 certified then it
must have that 40Gbps mode (which, snark aside,
is an improvement).
If you look at this comparison chart
carefully...
...you'll see it is comparing the
minimum requirements for PCS with TB4/TB3/USB4/USB3 branding, not the
maximum capabilities of those technologies. E.g. people are
already rocking
6K displays and
2m 40Gbps cables on their old TB3 ports - and 4K or better displays and 60W charging on USB-C ports - it's just that the minimum specs don't
require that.
All that fluff makes it as clear as mud what, if anything, TB4 can actually do that either TB3 or fully-tricked-out USB4 can't or if it is just a re-brand of TB3 (4-port peripheral controllers and having TB built in to the CPUs does sound new - but it's hardly a major upgrade to the standard...).
Still, what Intel is doing is a bit better than what the Lords of Confusion (aka. the USB IF, aka. the committee designed by a camel) with their "USB4!!! (actual USB4 not included)" branding. .