WSL: Unable to view the folders (appear as file) in Windows explorer if using symlink, but works if symlink on the same directory - linux

Question

No idea why but it seems that Windows explorer unable to view symlinked directories that the target is not on the same directory as the source target.
Is there a way to fix it? As it also make win32 applications unable to read the files under the symlinked directory. (I understand Windows equivalent mklink exist, but I need to do it in WSL's ln.)
Thanks a lot.
Sysinfo:
Windows 10 Pro 2004 Build 19041.264
(No idea how to check WSL build number)
WSL2
Subsystem uname: Linux PC 4.19.104-microsoft-standard #1 SMP Wed Feb 19 06:37:35 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Ubuntu:
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
Example:
$ pwd
/mnt/d/symlink_test/innerFolder
$ mkdir source
$ touch source/testfile
$ ls source
testfile
$ ln -s source target
$ ls -l
total 0
drwxrwxrwx 1 user user 4096 Jun 6 10:55 source
lrwxrwxrwx 1 user user 6 Jun 6 10:55 target -> source
Now view the output in Windows explorer:
As you can tell, the target folder is recognizable by Windows Explorer
As well as the file testfile is accessable in Windows Explorer
Counter Example:
$ rm -rf target #Just clean things up
$ ls
source
$ ln -s /mnt/d/symlink_test/innerFolder/source ../upper_target #make a symlink to upper dir, or any directory that is not in the same dir, with the source dir being absolute path
$ ls -l .. #List files on the upper dir
total 0
drwxrwxrwx 1 user user 4096 Jun 6 11:03 innerFolder
lrwxrwxrwx 1 user user 6 Jun 6 11:04 upper_target -> /mnt/d/symlink_test/innerFolder/source
$ ls ../upper_target
testfile
However, but now, if you view it in Windows Explorer, the upper_target will become a single file instead of a folder, like above: