@rebelliouswhiz,
No, it's definitely an RTL8157, I have multiple 6th Gen mini PC's here in my Proxmox cluster, all of those connect at 5000M (USB.3.0) and then I get the 3.3 Gbits/sec TX/RX and the connection is unstable. On the N150 where it connects at 10000M, it's rock solid.
Other points noted during my testing here, I have a 6th Gen Windows Mini PC and that RTL8157 is connected via a powered USB hub, that connection is more stable (doesn't drop the connection) than if the adapter is connected direct to the PC, however Tx/Rx is still 3.3Gits/sec.
I also checked on my 11th Gen laptop (which is supposed to have USB3.2 & USB4 ports, yet in that case even though the Windows shows it's connected at 5Gbe, the Tx/Rx is still at 3.3Gbits/sec in iperf3.
So with that I conclude that if the USB only connects at 5000M then the Tx/Rx rate will be 3.3. only AND that the power draw by the adapter is also having an effect on the stability.
Key for me was to get the N150 connected at as fast a speed as possible, so that issue is solved for me. For the other 6th Gen PC I have a couple of the RTL8126 PCI M.2 cards on order, which I will install in the WiFi M.2 slot, and I suspect that will provide the 5Gbe correctly (although it's not critical for my home lab).
DerekG