I wouldn't. His is probably continuing on despite the premature decapitation rather than because of it.

>Lots of 5-10-10 helps along with kelp<

Without conducting a test using control plants you don't actually know that your particular fertilization program is producing any one specific benefit. It might be for instance that what they are responding to is primarily the 5% nitrogen.

If you keep doing this same combination for years the 10% phosphorus might eventually start to become a problem, depending on how much P was already in the soil. And how much the kelp might be adding.

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/seaweed-extracts.pdf

I let mine grow naturally and they bloom quite a few times without doing any cutting sometimes I peal the old faded flowers for looks if they dont fall before I get to them but once I see flowers I usually keep them all season

If the plants are tended and the foliage remains looking good, I'd just leave them be.

If you have many of them, try the method on some.

This is one of mine but they all continuously bloom without Deadheading them and also I think it adds somewhat of a balance to the flowers cause they get so full they tend to lean over this way I find they hold up

Thanks to roselee and others for their comments. Sorry to relate...I am so inept that I can't post a picture. So..I have not yet cut any first bloom stalks to the ground. Still cutting the first bloom after it has faded and starts to show seeds. The sheath right below is hiding a new blooming shoot. After that one fades and is cut...there will be another sheath. Three is about all I get.

I leave all the foliage until winter, because it covers the front outside wall of the house and provides a nice contrast.