Why is the virtual interface limited to 10Mb/s?

Linux may show the ZeroTier virtual network port as a 100mbps or 10mbps port. This is incorrect. It's a software defined port with no intrinsic speed limit. Linux doesn't show accurate numbers for non-physical ports that have no actual interface device.

See here for some history:

https://www.phoronix.com/news/Linux-TUN-Driver-1000x