It may well not be vinyl, Spath. Some emulsions are sold as "contract" or maybe "trade".
These are non-vinyls made especially for new plaster which needs to "breathe" as it dries out. Vinyl would inhibit the drying process.
Not so easy to wipe down of course. One good thing is that they are much easier to over-coat. Plenty of times on a job, someone casually leans against a recently plastered and painted wall, leaving grubby handprints (usually plumbers.) I just paint over the offending area ;o)