I always thought this was determined by glassware. Some bars use the 2 oz Oxo measuring cup and are hell-bent on scaling the recipe to fill it. After chilling, this perfectly fills their coupe. But a bar with a 7+ oz conical "Martini" glass wouldn't be able to this without appearing stingy.
For my home use, 2 oz is a bit skinny, but anything over 4 oz is asking to be down-scaled or upped to yield 2 drinks. The drink you linked to has awkward proportions, so scaling it accurately would be annoying, whereas a Last Word or Negroni can be made in any desired size without mental gymnastics.
I don't object to smaller drinks at a craft bar because I'm probably having two and don't want too much alcohol. But I expect a fair (not cheap) price and high quality ingredients.
