Two things:
1. Are we sure the Crystal 150 the brewer refers to is 150 ECB? He never specifies in the interview and Chad uses Crystal 80L and misses the color by an apparently large margin. In another part of the interview the brewer states that he can never seem to remember ECB, does this mean he is more accustomed to and more likely to use Lovibond? In any case, I cannot make the color work out (targeting 13L from 32 ECB) in my brewing software with Crystal 80L but I can with Crystal 150L. Is it possible they're using the Simpson's Extra Dark Crystal in the ESB?
2. Either the recipe has changed recently (since 2005) or we're not getting the whole story. The head brewer at Fullers states in this article that the recipe for ESB is "91.5% pale ale malt (optic barley variety), 3.5% crystal malt and 5% flaked maize" I'm not suggesting subterfuge but did want to point it out.