With great masochistic enthusiasm, I always enjoy these kinds of tales from the almost-tropics so near by, but yet so far.
I do have some advantage in the humidity area with gas heat. It doesn't dry the air like a central system so the only really dry days are those intermittent ones when the lack of humidity outside dries the indoor air too. Those days when I notice static in my hair and on my clothes. One of the worst feelings, can't stand that! The average humidity here all year is pretty high, so those dry days are thankfully rare.
If I had dry air all winter, I might be having a different experience with bringing Ti inside. I can remember having static hair all winter when I lived in OH because I always had central heat that dried the air terribly, but no Ti plants until after I'd moved to AL.
I'm not in FL, don't have a GH, and am in Z8 so bringing them in here is the only way to ensure survival. Most of my grounded Ti plants survive in most spots, and then they grow back 1-2 feet tall until they get frozen again. A winter could come that wipes all of those out so I've had some inside for the past 12 winters. If I want to have any more than 2 feet tall, winter protection is necessary.
I would be surprised if Cordylines are in any danger in Z10. But it did strike me as interesting that a plant that seems bulletproof to me is described as iffy elsewhere, and that bringing one inside would be tried. I don't bring anything that is reliably hardy here inside unless I'm using parts that would otherwise get wasted by winter to propagate to add to the landscape, like Brugmansia, Lantana. purple heart Tradescantia, confederate roses, rhizomatous Begonias, Kalanchoe blossfeldiana - all herbaceous perennials here. Cordyline is not as reliable as those when it comes to not being killed over winter.