Sweet pea and Braille

This 2008 stamp should be the model for all postal operators and philatelic agents.

The sweet pea (Lathyrus odoratus), Finland, 27 February 2008.

If you watch carefully this scan (or check the WNS reference), you can see the Braille dots that I imagine recall the stamp denomination...

... yes, without any reference to Louis Braille, or a blind-care association. Like that.

When does the generalisation begin? At least in countries where sending a cécogramme is not free of charge.