It seems that the buff is indeed a harcoded value:

When I ask to see a screenshot or a copy-pasted value that you use, is just because sometimes things can get messy on tiny details: lowercase problems, spacing where it should not have or a typo, a letter in place of another. But if you are sure that you made it right, then let's skip this. Also that would not work for you anyway.
Is there any way to do a quick update to the plugin or modify the code slightly to modify cparams by a set value, either in skills or states?
- You can do that with cparams, or any other parameter using this plugin:
Hakuen Studio Dynamic Parameters for RPG Maker MZ by Hakuen Studio
Youi can use the states note field to dynamically change the parameter of a battler.
My dynamic template

state applies fine using my skill, but upon going to the status menu where Physical attack is displayed, i get this error

