There's a couple of different reasons that I might not pair up those two.

First, cabbage loopers also will feed on dianthus, so planting those two types of plants together will just make that area doubly attractive to cabbage loopers.

Secondly, cabbage is fairly thirsty and likes consistent watering in order to grow the big huge, spreading plants they eventually become. Carnations don't like too much water except when the weather is really hot and they need it in order to survive. I have some concern that their water needs might not be a good match.

However, you'll never know for sure how they will do for you in your soil and with your rainfall/irrigation techniques unless you try it yourself. Soils and rainfall vary so much in Oklahoma that sometimes you just have to try things to see what works and what doesn't. Just because something does or doesn't work out as planned one year doesn't mean you can expect the exact same results in every year because one year you may get 24" of rain and another year you may get 30" or 40" of rain.

If you do grow them together, remember that cabbage is an annual and will be gone in a few months while carnations are perennial (if they survive the summer heat) and be sure you select a succession crop to follow the cabbage that will be compatible with the carnations' need for more water in the heat.

I grow perennial dianthus in my garden as companion plantings so always have to consider their needs when I am deciding what to plant near them. in any given year. Because I have slow draining clay, I only grow dianthus in raised beds with highly amended clay and, even then, they are short-lived perennials lasting between 2 and 5 years for the most part, and how long they survive just depends on what the weather does. Carnations seem a little pickier about soil and water than regular dianthus and also don't seem to tolerate our heat quite as well.

It's like a decorative cake that's too pretty to eat. hahaha

It's perfect for flowers, but too rich. Cabbage deserves it. I'll use it for flowas after it's spent. :D

Yeah, if it is too rich, your flowers might give you only vegetative parts and not a lot of blooms. It just depends on which nutrients it is rich in.