You may be accustomed to sellers whose standard statement for most of their stock is "Great Vintage Condition" or "great considering its age".
When you receive your purchase from them, perhaps you notice a little stain here, and a few pinholes there, and you count your blessings that there's nothing major - you would have happily paid the same price if you had a chance to inspect it first.
Or maybe the seller didn't mention the 1" hole in the back of the skirt or the yellow stains under the arms and now you have to decide whether to question their interpretation of what constitutes "great vintage condition".
You might have bought it anyway if flaws had been fully described, but maybe not. Or maybe not at the price you paid for the blithely described "Great Vintage Condition". Those sellers may justify themselves by saying "All vintage is flawed, you should expect it". I have a hard time trusting the sellers who never seem to have flaws to report.
Here's what I would say: Mint condition is extermely rare when it comes to vintage items, even New Old Stock. Just because it hasn't been worn doesn't mean that there might not be some dust from long storage or some fading.
And most vintage clothing
I inspect everything I sell several times. I'm going to tell you about anything and everything I find, because I want you to make an informed decision before you buy. I try to take close-up photos whenever possible of flaws I am describing. I'm more forgiving of flaws in older garments in terms of offering it for sale, but I'll give you a detailed condition report. And check out my Not Too Shabby collection!