I don't see how "inconclusive" means conclusive...
If the FBI only has a few markers, then it's likely a sizable plurality of the population will match.
P(A:B)=[P(B:A)P(A)] รท P(B)
Back in 2001 the FBI was working with 13 DNA locations. They did not get results for all 13 locations with DBC. I do know the number of locations they got.
Also, there were multiple donors. Therefore, some locations have DNA markers (numbers) for more than one person.
If a suspect comes along and does not match all X number of locations the FBI has then this person cannot be DBC.
On the other hand, if a suspect comes along and does match all X number of locations then this person cannot be eliminated. Importantly, this person cannot be confirmed as DBC because some locations have more than one person's DNA and they cannot separate the DNA samples.
So, an "inconclusive" result shows that the person cannot be eliminated, but also not verified.
Now the odds of a random person matching all X number of locations is difficult to determine--I have discussed this with a DNA expert. However, the odds are still thin and likely well under 1%.