I have an idea. Why don't you ask your flooring person to apply some to a piece of flooring so you can judge for yourself? If he balks get you a new floor person.

Check the manufacturer's product data sheet (or call their help line to ask.) Sheen is measured on a 0-100 scale. Below 5 is usually considered dead flat, and 85+ full gloss (glosses higher than that need buffing). There is no uniform definition of "semi-gloss" or "satin" either between brands or between different products of the same brand. Even then, there are manufacturing variances and you will normally get a number range, something 45-50 sheen for a specific product.

For example, Bona's Traffic Anti-Slip Satin has as spec:
Satin sheen of 25 at 60ð ( 60ð being the viewing angle (angle of incidence))

Here is a link that might be useful: Sample