I'm not sure of its significance, but after the first use (on a groundsheet, on nice soft grass), I noticed a flaw in the floor as I happened to hold it up to the light in the right spot as I was folding it up. It's only visible when held up to the light. I can't feel any difference from the surrounding fabric (which is actually the normal grey, not black), either on the inside or the outside - but I'm not famous for picking up things like that. I'm hoping it's just a fault in the dyeing process, and not the water-proofing process.
Unfortunately, the shop I could get to that had it in stock is one where I've experienced poor customer service on multiple occasions. I usually avoid them. Henry at Wilderness Equipment is apparently no longer taking calls or emails directly from the public, to free up more time for his main work -even though it still says to contact WE directly in the current tent info. Apparently that's why he hasn't been returning calls or responding to emails for a while.
Sooo I wanted to get a bit of an idea about what folks think is the issue before I contact the not-helpful people I bought it from. Thanks a bunch for your thoughts.