The plant tag was correct. The grass is a perennial where there is no ground freeze. That doesn't include your zone, so for you, it's an annual. Many gardeners in northern climates use them as annuals, buying new ones every year.

It seems that is correct. However, the plant tag says "not subjected to freezing." And Lowe's indicates a 1-year guarantee. Now I just think they wrote this tag wrong, or it should have gone to a store in a different zone. I think I will return the 10 plants anyways based on what their tag says.
Thanks for your help.

I'm not sure what you think was misleading about the tag - it seems quite clear to me that it indicates this grass will NOT act as a perennial in areas subject to freezing temperatures (anywhere below zone 10). Obviously the know-nothings at Lowe's gave you conflicting and incorrect information and you are certainly justified in acting on their guaranty.

FWIW, Lowe's and the other box stores consistantly sell plants outside of their hardiness zones, so it is a case of buyer beware, especially as you will never get knowledgeable information from any of their so-called "garden professionals" - however, since they do so with a 1 year guaranty, you may feel it worth the risk (and the effort) of replanting annually. Believe it or not, the return rate and the refunding under their guaranty policy is really very low.

Pennisetum setaceum 'Rubrum' is considered an annual and not winter hardy pretty much everywhere in the country except for Southern California and parts of the deep South.

It is what it is...a low cost super center, without the service knowledge of a specialty shop/garden center.

Their 'garden pros' know as much of gardening as I do about plumbing (long story).

If you want to buy plants from a big box store and aren't sure, go home look the plant up in a book or internet and return to buy, armed with your own knowledge.

I agree, the tag sounds like it did make sense and accurately described a tender perennial.