This feature has been removed in version 2.17!
The only purpose it did serve – more than 20 years after its introduction – was to confuse users needlessly.

This option only has an effect if the supported bit depth of the WDM driver is larger than 16, but less than 24. Some devices report e.g. 20 Bits resolution but cannot actually be opened for more than 16 Bits resolution. Should this be the case on your system, this option provides a workaround. Originally, this was introduced as a workaround for an issue with the SigmaTel AC97 WDM driver.