Circling To Land On NDB-B and NDB-C

I am new to this group, because I recently went through an IFR course.

I do have a question. There is an airport close to here called Orlando
Sanford (SFB). It has two approaches called NDB-B and NDB-C. Both are
similar but they approach the airport from west and east, respectively.
Let's consider NDB-B. The approach is on 095 to the NDB, which is located
just north (very close) to 9L. The airport has runways 9L, 9C and 9R from
the west, plus a north-south runway. I asked my DE why this approach was a
circling to land only instead of a straight in approach, since the approach
course and runway 9L are well within 30° of each other. It took him a while
to say that the reason is that the approach doesn't cross the extended
centerline of runway 9L and therefore, it is a circling to land.

Now this sounds great, but I have not been able to find any reference to
this in the literature. I can only find references to the "within 30°" to
define a straight in approach, but I can't find that it also has to cross
the runway centerline. Can anyone help me out on this?

Thanks.

Simon Ramirez
Oviedo, FL