This doesn't mean that sensing with vibrissae is a type of vision.
As with most predators, their eyes face forward, affording depth perception at the expense of field of view.
Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction.
The other protein, TAS1R3, is present and identical to that of other animals, and the relevant taste buds are still present but inactive.
Such a genetic marker found in the entire family and not other animals must be the result of a mutation in an early ancestor; as a deletion mutation it could not revert, and thus would be inherited by all descendants, as the evolutionary tree branched out.
While this improves the ability to see in darkness, it appears to reduce net visual acuity, thus detracting when light is abundant.