Comment # 4 on bug 1182592 from Neil Rickert

I can confirm this.

I setup a KVM virtual machine to test it.  I first installed Tumbleweed.  Then
I set GRUB_DISTRIBUTOR=opensusetw
in "/etc/default/grub", and used Yast bootloader to update the settings.  That
gave an "opensusetw" as in EFI boot name.

Next, I installed Leap 15.3 in a separate partition.  And that install removed
the entry for "opensusetw".

I then tried it the other way.  I change the boot name for Leap 15.3 to
"opensuselp" (using GRUB_DISTRIBUTOR).  Then I booted into Tumbleweed, and set
"GRUB_DISTRIBUTOR=".  Using Yast bootloader to update the configuration (I
change the timeout by 1 second for that) and the "opensuselp" entry was
deleted.

It looks as if bootloader install is removing all entries with the string
"opensuse" whereas it should only remove "opensuse" and "opensuse-secureboot". 
To me, it seems reasonably sensible to use names like "opensusetw" and
"opensuselp" as alternative names, and we should not expect those to be
removed.

If I use GRUB_DISTRIBUTOR=Tumbleweed
and GRUB_DISTRIBUTOR="Leap 15.3"
then there isn't a problem.  Likewise, if I set UPDATE_NVRAM=no
in "/etc/sysconfig/bootloader" then there doesn't seem to be a problem.