I heard that too, so I bought one this year. Too early for me to tell about spreading, but it did bloom a really nice long time (and is on some reblooms now).

I found 'Miss Manners' was not very vigorous in my garden. In fact, I have bought three different plants at various times, and my one remaining plant died last winter. The variegated obedient plant can be a bit temperamental as well. I had it for many years at my mom's house. only to have it die out on me here (same city, different house).
I can't vouch for its growing habits in your area of zone 9. but you may get more bloom out of it than I did.

I planted 3 'Miss Manners' 5 years ago. They have behaved themselves very well.

On the other hand, 'Vivid' that was supposed to behave, has spread like there's no tomorrow. I am in despair in trying to get rid of this one.

I've planted probably 10-12 of them in my wet clay woodland border. They are lovely in bloom, I hope they spread a little bit next year because I have them in a moongarden of sorts.

From what I've read, they are native to Illinois and probably won't get out of hand, especially in the clay.

Good luck with yours. :)

I forgot to mention that I have 'Vivid' (a short, very late-blooming one) and 'Summer Glow'(closer to the wild variety). I have both in quite a lot of shade, so they survive for me, but don't spread out of control. 'Vivid' blooms into October here.

I love Miss Manners. It is a clump former, not a runner. I grow it in a semi-bog area and the clump has doubled in size in a year. I also grow the species and keep it under control by growing it in a south facing bed that has only moderate moisture plus it has competition from phlox 'David'. Under these conditions it acts like a clumper. However, I'm sure if I moved it to my boggy area in the back it would take off.