WashesWhiter is a spurious product feature used to justify the development of a new product or internal tool, or to argue for the replacement (or retention) of some tool that the speaker is particularly keen on.

The feature makes no contribution to the way the tool or product will be used, but its absence from the competing products is claimed to be a reason for rejecting them.

WashesWhiter because the phrase occurred in well known detergent adverts in the UK (at least). US readers may prefer TastesGreatLessFilling, or does that have other connotations?

Don't forget LemonScented either. ''That is best for the U.S.A. as meaning "this is a fluffy feel-good claim".''
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In Germany the slogan was "Washes whiter than white". That was in the 1970ies.