The .bat script is executed by CMD, so the Windows 11 taskbar
groups both together in one icon group.
The Windows 11 taskbar doesn't support the option of “Never Combine”
taskbar icons which was found in Windows 10, so doesn't offer any
solution except that of executing the script using another handler,
for example PowerShell.
Another solution is to replace the Windows taskbar by a third-party
taskbar product in order to regain this option as in Windows 10.
These products emulate an evolved version of the Windows 7 taskbar.
If one can believe the article
Windows 11’s “Never Combine” taskbar icons feature is coming in the fall,
dating from March 16, 2023, this will change in an upcoming upgrade.
The article says:
According to sources familiar with the development, Microsoft is
finally working on returning the ability to ungroup taskbar
icons/items or buttons. The feature is called the “never combine”
Taskbar, which was first added to the OS with Windows 7.
With this feature, you can restore the classic Windows 10 behaviour
where the same app won’t be grouped under one icon.
The feature is coming in the fall, and Microsoft is also restoring the
ability to show app titles, which was removed with Windows 11 21H2.
The never combine option is present in the public builds, but it
doesn’t work now, and codes to make the feature work are missing.
For the moment, your options are either to wait for the next release
which might possibly be named 23H2, or use a third-party taskbar in the
meantime.
