[grifferz]

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!