Indeed. That file is auto-generated using default values that work for almost everyone. It cannot be edited manually.
It isn't a problem in as much as this is the first time I've ever seen anyone ask about it.
It's clearly a problem for you because you're using a custom client side config.
A solution to that would be to carry a custom patch in pfSense that changes the default values used to generate the file so it works for you.
And/or you can open a feature request to expose those settings in the gui,
