Well, all beta testers and vendors are not created equal :)

Some vendors have a specific itemized list of what they want their testers to look for. Others just leave it up to the tester to do their own thing.

And then there is the experience of the beta tester. A beta tester is only as good as the people they test for. If a tester doesn't know to do certain things or look for certain things and the vendor doesn't tell them, then the tester doesn't learn, the test is shoddy and the vendor is unhappy.

So IMHO it's well worth it for the vendor to talk with their testers initially and tell them right up front about what it is that they expect them to test for and look for.

IE:

what version of Poser are you testing in?
proper license
informative readme
proper file structure
absolute paths
missing files
version number errors
hard seams (not only at the usual visable places but places like between fingers too)
texture stretching
what about second skins? Do they bleed or smear at the edges?
holes in the mesh
props that don't follow the pose
intersections
other errors or anomolies when loading
any problems rendering?
does the item render settings need something special like turning off texture flitering or using Poser4 render instead of Firefly? Are those instructions listed in the readme?
is there anything about this package that you feel could be improved upon in order to make it more user friendly?

There is a great deal for a beta tester to look for and check. It's not just a matter of  whether the files load or not.  And a vendor shouldn't automatically assume that a tester knows what to test for. A vendor should expect a tester to look for all of the above and their  report should address all of the above and images of problems found should accompany the report.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi