Can one be "taste blind" to the sweetness of stevia?
There's some variation in how people respond to Stevia:

From 2013: Multiple genes manage how people taste sweeteners


  another study recently published in the journal Chemosensory Perception, Allen had 122 participants taste two stevia extracts, RebA -- Rebaudioside A -- and RebD -- Rebaudioside D. Stevia is a South American plant that has served as a sweetener for centuries, according to the researchers. While the plant is becoming more popular as a natural non-nutritive sweetener, consumers have reported a variety of tastes from stevia-based sweeteners, including bitterness.


No mention of people not tasting the sweet at all, but it is a big gene pool.
In me, the stuff is a slow,tight binder. It takes a while for the sweet to come on once I've eaten the stevia, and it takes a minute or two for the sweet to wear off after I've had it.