Randomized Content Block Problem Type filter bug?

I’m using Tutor v14.05 Nutmeg.

What I did was:
I created a library with 20 multiple choice problems.
I created a Randomized Content Block component and set Count = 20 and Problem Type = Multiple choice, but I got a message that said “The specified library is configured to fetch 20 problems, but there are only 10 matching problems”. I change Problem Type = Any Type and it worked fine.

Is this a bug or did I miss something?