System Information on my MBP says "Thunderbolt/USB 4" in its sidebar, but doesn't say anywhere that it'sThunderbolt 3. (Mactracker tells me that.)
And add to that the facts that
A Thunderbolt port is the same as a USB C/4 port,
Mactracker tells me that my Thunderbolt ports support USB 3.1 Gen 2, but as far as I can tell, USB 3.1 Gen 2 is really USB 3.2 Gen 1,
and a USB drive plugged into a Thunderbolt port with an adaptor shows in System Information as utilizing a USB Bus but not a Thunderbolt Bus.
And I forgot to mention that USB 3.1 Gen 1 is actually the current terminology for USB 3.0.
It appears you are conflating connector types, ports and protocols. USB A, USB B, USB B micro, USB B mini, and USB C are physical connector types
and each type is related to one or more protocols
. Thunderbolt is a specific variant of USB. By specification, each protocol is backward compatible with the preceding protocols but particularly in USB 2 and USB 3.x there are multiple options including minimum and maximum power delivery, the number of data lines, and the maximum and minimum data speed of each of those lines. This Wikipedia chart
shows the relationship between connector types and protocols. Note there are three type A connectors with either 4 or 8 actual lines depending on the protocol they are used with but until recently the standard did not require the protocol to be specified on the connector. Note too, the USB type C port is specified for use with any USB protocol but USB 1.0, so instead of USB C/4 it should be USB C/2.0,3.0,3.1 gen 1, 3.1 gen 2, 2,O, 4.0, Thunderbolt 3, Thundebolt 4. Much of the confusion revolves around the fact that with the release of the USB 2.0 standard the naming convention was changed as shown in this Wikipediia chart
. For whatever reason it has taken many vendors a long time to catch on to the change, but over the last year, I have noticed that most have caught on, and I avoid those that seem unaware.
The Thunderbolt 4 specification requires full backward
compatibility with USB 4, but the USB 4 specification does not, and should not, require forward
compatibility with Thunderbolt. So you can connect any USB device to a Thunderbolt 4 port and expect it to work, but not vice-versa
. However, when a USB device is connected to a Thunderbolt 4 port the port is limited to the lowest connected protocol, ie.
USB 4 and will appear that way to the system.
In case you are wondering, Thunderbolt and USB were both developed by Intel, but Apple had significant input on the Thunderbolt standard.
By-the-way, unless you have a Mac with Apple Silicon, the thunderbolt port is Thunderbolt 3