Hello Ornen
Let’s start by saying that the value of functionality_storage (let’s call it FS for short) is not used by Google Analytics nor Ads. Google’s documentation does not even mention it. Here’s a link https://developers.google.com/tag-platform/security/guides/consent?consentmode=advanced#gtag.js_1
However, the value of FS can be used by tags that are loaded via Google Tag Manager. Documentation link https://developers.google.com/tag-platform/tag-manager/templates/consent-apis#implementation_example
However, Google is very unclear about the default value of FS. I don’t think I remember seeing them recommend its default value.
One can argue, that this should be always set to default, since functionality = necessary. However, if so, then why is this value there in the first place?
However, if you look at it from a different angle, “functionality” can be used for personalisation purposes too. And since Personalisation is one of the categories of consents in WP FP, setting it to “granted” by default, would lead to setting up some non-essential cookies and collecting non-essential data.
I hope this makes things a little bit clearer.
Have a nice day
Krzysztof Planeta
Author of WP Full Picture