Interesting. Thanks for the headsup regarding WSL import/export.
I've not actually tried it as yet as I have not had the need to backup WSL and move to a new machine. Generally, I just install from fresh and start again
I wonder if the "different user" thing is a result of different UID's being created in the new instance? 
What I do know is that you can start a WSL distro using a specified username, by using the --u or --username arguments. Refer: https://winaero.com/blog/run-wsl-linux-distro-as-specific-user-in-windows-10/
Also, you might be able to change the "default user" that a distro will start up with, depending on the distro you're using. With Ubuntu, it's something like "ubuntu.exe config --default-user MYUSERNAME". But you need to figure out what distro you're running. refer: https://docs.microsoft.com/en-us/windows/wsl/user-support
I've not actually tried it as yet as I have not had the need to backup WSL and move to a new machine. Generally, I just install from fresh and start again
I wonder if the "different user" thing is a result of different UID's being created in the new instance? What I do know is that you can start a WSL distro using a specified username, by using the --u or --username arguments. Refer: https://winaero.com/blog/run-wsl-linux-distro-as-specific-user-in-windows-10/
Also, you might be able to change the "default user" that a distro will start up with, depending on the distro you're using. With Ubuntu, it's something like "ubuntu.exe config --default-user MYUSERNAME". But you need to figure out what distro you're running. refer: https://docs.microsoft.com/en-us/windows/wsl/user-support