EUSS family permit application dependency

Hi, need some advise please.
Am a British citizen and my wife is an EU national, we have been married for couple of years and have children, my wife have applied already to the settlement scheme and obtained a reference number.

We are in the process of applying for an EUSS FAMILY PERMIT for my parents to join us, who are non-eu national.
So regarding the dependency point, it says in the guidance that it is assumed for this application, so how lenient the home office regarding this point. And do we still need to prove it, and how.

And what documents please you advise me to submit and support the application.
Note me and my wife are both full time working, and have financial security.
Many thanks for the advice.