The term " venitian plaster" is probably confusing the contractor. An experienced stucco finisher can offer a wide variety of textures. On a traditional stucco topcoat, you can have light to heavy texture options, while the newer acrylic/elastomeric topcaoats are limited to fine. If you are in an area that has constant freezing in the winter and major temperature changes throughout the year, i'd go with the acrylic as it flexes, (expands/contracts), with those changes and lessens the chance for cracking. Either your contractor is inexperienced or simply doesn't want to mess with texturing, but either way, again, an experienced finisher can offer a multitude of patterns.

Here is a link that might be useful: topcoat pattern samples