At MatterHackers our customers are important to us, and we try to be as flexible as possible when it comes to quality control issues like the one you describe. It doesn't sound like you bought this filament from us, but if you ever do please keep in mind that we want to hear from you if there's ever a question of quality.

That said, 30 days seems a bit short for a warranty but I don't see anything underhanded or necessarily wrong with it. It's reasonable enough if the seller makes this absolutely clear and you agree to purchase the product.