Tried enabling and disabling this plugin and the other Creality temperature plugin to see if it would make any difference but it didn't.
Googled but didn't find a solution that seemed to fit.
This is the intended behaviour. It only rewrites the lines internally for parsing by OctoPrint, the actual communication from the printer can't be changed by the plugin, which is what you are watching in the terminal. You will be able to tell it is working if the temperature graph works properly now.