I don't see why people on modern machines need or bother with GRUB when EFISTUB exists. The UEFI boot manager should be all you need.
I have configured password protection for my UEFI settings (so that a potential attacker could not easily disable Secure Boot, for example) and GIGABYTE's UEFI implementation requires that password for the boot manager as well. In other words, when booting using this setup, I need up to three passwords: 1. UEFI password, 2. Disk encryption password, 3. User password.
Hence I use systemd-boot to set BootNext and reboot into the Windows boot loader.
Another reason for having a bootloader is that you may have more entries than the built-in manager can handle, for example if you can boot into automatic snapshots.
Each operating system has its files in their respective directories on ESP, and each operating system registers its own boot entries pointing to bootloader in these directories. With UEFI, there's nothing to overwrite, except setting the default entry.
That's not an issue, since you can both easily boot non-default entries and change, what the default entry is.
So it does what is expected from any boot loader. Installing grub does the same.
> And since their installer does not add other OSes to the Windows bootloader automatically
Which is fine; you should not chainload windows from grub either. Use ntldr for booting windows.
> you have to either change your UEFI settings
Exactly, you can change the default boot entry in your UEFI settings.
Or after POST, press a button on your keyboard for one-off boot change.
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So what was the complain, again? Some people not using UEFI boot manager in a way it is supposed to be used?