Is there an explanation for the non standard source level potentials?

[Question]

Mainly in Tuarhievel and Sielwode. Elven provinces dont reduce source level potential per the original rules, but the potential in elven provinces are too low. Fhylallien's potential is only 5, which is the same as plains. It's in the middle of the Sielwode, so one could argue that it counts as a "deep forest" with a potential of 9. Even a regular forest has a potential of 7 and all the elven provinces have a potential of 6 at best.

The original rules do say there are "exceptions", is there any explanation for why the potentials are lower than they should be?

[Sorontar]

Mainly in Tuarhievel and Sielwode. Elven provinces dont reduce source level potential per the original rules, but the potential in elven provinces are too low. Fhylallien's potential is only 5, which is the same as plains. It's in the middle of the Sielwode, so one could argue that it counts as a "deep forest" with a potential of 9. Even a regular forest has a potential of 7 and all the elven provinces have a potential of 6 at best.

The original rules do say there are "exceptions", is there any explanation for why the potentials are lower than they should be?

I believe that the normal explanation within the community is that the rules are for making new maps/provinces, not understanding existing ones.

Sorontar