I didn't know about this "feature", but to be honest I have learned years ago not to use the partitioning features of the debian installer. It's just another crude tool to fight with, while the real tools are just a console away.
Here's a list of the things the debian-installer can't do, or at least couldn't do when I needed it:
- accurate partitioning, such as choosing between GPT or MBR partitioning
- filesystem features (btrfs subvolumes, ext4 flags)
- creation of crypt volumes with keyfiles
- having user control over the names of crypt devices
- using an existing crypt device WITHOUT formatting it
By choosing "expert" mode you can choose between any of the partition types (much more besides mbr and gpt). In standard mode it will pick mbr if none of your devices are bigger than the mbr partition limit (2TB?) otherwise it will pick gpt, without offering you a choice.
You can choose expert mode at the start when you boot the installer or you can switch to it from the menu once it's started.
I think you may be right about the other things, but this is not uncommon amongst OS installers. It is very hard to offer the full range of configurations available from all of the tools used to install a Linux system, without just putting the user at a shell prompt and letting them get on with it. Luckily that option is still there!
Here's a list of the things the debian-installer can't do, or at least couldn't do when I needed it:
- accurate partitioning, such as choosing between GPT or MBR partitioning
- filesystem features (btrfs subvolumes, ext4 flags)
- creation of crypt volumes with keyfiles
- having user control over the names of crypt devices
- using an existing crypt device WITHOUT formatting it
- mdadm write-intent bitmap enabling/disabling