Q.Why My T. Fortunei Has Grown A Lateral Secondary Xylem/stem?
I can email photos

Certified GKH Gardening Expert
In the case of T. Fortunei, the growth of lateral secondary xylem or stem can be a sign of stress or damage. This isn't necessarily any cause for concern unless the palm looks stressed. This, also, can be something from the past.
You can propagate them, or leave them as part of your tree.
Here are some articles that will help you:
https://www.gardeningknowhow.com/ornamental/trees/windmill-palm/propagating-windmill-palms.htm
https://www.gardeningknowhow.com/ornamental/trees/windmill-palm/growing-windmill-palms.htm