Negadoctor manual: erroneous scan exposure bias recommendation?

For Darktable’s Negadoctor, the user manual (4.8) states that if you want to correct the shadows color cast, the scan exposure bias (in the film properties tab) has to be zero:

“Note that the shadows color cast setting will have no effect if the scan exposure bias setting in the film properties tab is set to a non-zero value.”
darktable 4.8 user manual - negadoctor

However, it is actually the other way around: scan exposure bias must be at a non-zero value for the shadows color cast setting to take any effect.

Of course, you don’t necessarily need to correct the shadows with every film stock, but for a long time, I erroneously kept scan exposure bias at zero because the manual may be misleading in this regard.

Did I misunderstand something?

Edit:
Even an early introduction states that

“To use it, make sure that the exposure bias of the scan, in the “film” tab, is not zero or the setting will have no effect.”
darktable 3.2: containment effect! | darktable

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