To be fair, you guys might be talking about two different things. Sure, the book is a standalone with regard to having a complete story-arc (and that it
could technically be read without any of the previous material), but that doesn't mean doing so would give a reader the best experience possible. There's things from the previous series that can affect the enjoyment/comprehension of this stand-alone ... and I'm sure there are things in this stand-alone that may have some bearing on later "stand-alones." I'm a bit of a purist when it comes to the term. I don't want to know if a book
can stand alone, I want to know if it
does... in every way imaginable (meaning no connections to or from other books).
The point being: if there's any possibility that a group of loosely-connected stand-alone novels will eventually become part of some sort of cohesive "whole"... then they're not stand-alones. Which means I'll probably wait until the "whole" is available.
But that's just me.