No, the M3 does not support this either. My next SSD will probably be a T7 again.

Although the Apple M3 chip supports USB 4, this does not necessarily mean that it also supports USB 3.2 Gen 2x2. USB 4 and USB 3.2 Gen 2x2 are different standards, and compatibility depends on the manufacturer's specific implementations. Apple has not yet released any Mac products that explicitly support USB 3.2 Gen 2x2 Although USB 4 can theoretically achieve the speeds required for USB 3.2 Gen 2x2, this does not automatically mean that all USB 4-capable devices also support USB 3.2 Gen 2x2. Apple is certainly going its own way with the implementation. The best thing to do is to ask Apple Support.

Well, I have read this question here. It's probably no different with the M4 (pro). I need a new external storage device for the Time Machine backup. The T7 should be enough for this and it looks a bit more discreet than the T9.
To copy large data, I use an OWC enclosure with a WD Black SN850X. That's too expensive for my backup.

I own an MBP M2 Pro and create my Time Machine backups on this SSD without any problems. The only downside, however, is that the data transfer speeds claimed by Samsung cannot be achieved because while Thunderbolt only has 1 lane, USB 3.2 2x2 has 2 lanes. If speed is important to you and you plan to use your SSD only with your MBP, I suggest you buy a more expensive Thunderbolt SSD like the Lacie Rugged Pro.