The form library is one shared copy per form, read by everyone in the brokerage. That's the point — the broker fixes a form once and it reaches everybody.
It also means editing the form itself changes it for everyone.
To differ on your own: select a plain field and use Just for me in the Properties panel. Set your own default value, or hide a field you never use. It only affects documents you create.
The shared form is untouched, so the brokerage's later fixes keep reaching you — which is what makes this better than taking your own copy of the form. A copy goes stale the moment the broker fixes something.
Reset clears your override and puts you back on the firm default. There's no copy to go stale.
Brokers and team leaders can also move the brokerage default, which changes it for everyone who hasn't set their own.