As far as I understood it's this:
All tastes, sweet, acidic, bitter, salty, umami,
happen to take place in different parts of our tounge.
Therefore, Riedel have developed a substantial variety of glasses providing as many different "angles"
at which the wine "hits the spot" as there are different wines if that makes sense.
As a simple example, if you were to taste any given wine from both their Bordeaux and their Burgundy type of glasses
you will find that almost always one will work better than the other.
Riedel have committed to seriously scientific research on this...
And, I am not an endorser for them, I just happen to live only a couple of miles away from one of their facilities
Viva Austria!
Cheers, Alex