Help with F '14 Liege

[Lohengrin]

The defense value of Ft Barchon is correct in both scenarios. In the getting started scenario, that fort is destroyed and vacated, hence the half defense.

Got it. Okay, but my next question would be: What about the forts that do start at -30%+15, like Fort Evegnee? Are these forts damaged in some way to start? In other words, what is the reason some forts have the lower value as opposed to the -60%+30 at the outset? Purely a historical question about the nature of this ring of forts which I'd [rightly or wrongly] assume to be of uniform and contemporary construction.