All good, dude! Selvedge will look like this:
Doesn't have to be red. The seams are very distinct, though.
Thanks to @Koala-T and Nat, I know a. what store to avoid after work today because it's already cleaned out, and b. not to skip obscure Nils hardware. They must have repriced that too, was way, way more than $25 when I saw it + I assumed Sonos had made multi-zone receivers obsolete.