I am fooling around before lunch with Data Base and I found (in less than 5 minutes):
a. There is no default file type for any of the built-in Data Bases.
b. FileTypeGroup:
I add one, then I wanted to look at the docs | documentation what I have to fill and where…
but a Search in the documentation returns nothing as you can see below:
And this question comes in the forum; I recall Greg answering one of these nor too far ago (but I forgot the answer… 
).
I will try the user guide(s)…