Well, yes and no...
You should have a moisture meter as a new burner, to get a sense of what you're burning. Over time, you will find you stop using it, as you build a nice stockpile of seasoned wood, and a feel for what's dry vs. not.
However, if this seller's wood ends up being over 20%, what are you going to do? Do you have another seller to consider? The reality is that 99%+ of reports we see here indicate that sellers advertising dry or seasoned wood don't understand the meaning of these words. Most are selling wood from trees that may have been on the ground over 1 year, but most often split just days before delivery. Wood doesn't really dry very well, until it has been split and stacked.
I read frequent advice here, people suggesting you take some of the seller's wood, and split and test it at time of delivery. I can't imagine actually doing this, or what I'd plan to do if it came in high. I think we'd do better suggesting people check out Poindexter's threads on how to dry wood insanely fast, he has set a new bar for this forum to match, at least in the speed department.