Originally there were no build modes. And then it appears when they were added no one bothered to create new defaults...
You could create a bug report. Not sure how quickly that will or will not be picked up.
There are also other issues, like the "which dwarf do you want question" => Different versions of fpc have different defaults, and the defaults differ for different target OS....
So the IDE does not know what the default is.
Also forcing a common default from the IDE will no always work. And the setting may need to be changed depending on if the user chooses FpDebug or GDB (or LLDB on Mac).
Worse, (and even the current dialog does not manage that). The primary setting (in project options) only affects project files. The LCL has its own settings. So if you debug into the LCL you may have to change those too.... (same for optimization).
Currently that means the IDE will then rebuild the LCL (and other packages). That is slow...
To fix all that is a huge task.
And also not simple, because with all the debug options in existence there would then be a need for several pre-build versions of all of that. But ideally not to increase the download size to double.
And I have no idea how it would affect prebuild closed source 3rd party add ons.
The list goes on and on.