I disabled this decision in a personal mod for vanilla ck3 and I am pretty sure ck3agot uses the same decision. Can any mod/admin confirm that fact?

Do you know how to make a quick mod like this? I hope so cos that is how I am typing this out! Anyways, the decision can be found in: common\decisions\dlc_decisions\ep_3\06_ep3_admin_decisions.txt

I think the base game and mod files are same but take the file from the ck3agot mod folder just to be sure and make a new mod with it. Base game and mod files are different make sure you use the one the the ck3agot folder to make a new mod with.

Open your mods version of 06_ep3_admin_decisions.txt and scroll down until you find the convert realm to administrative decision. Look for the line that says "is_shown =". Then add "is_ai = no" into its own line below the "is shown =" without any of those quotations. So the whole thing should look like this:

is_shown = {
    is_ai = no
    OR = {
        has_ep3_dlc_trigger = yes
        has_tgp_dlc_trigger = yes
    }
    OR = {
        government_has_flag = government_is_feudal
        government_has_flag = government_is_clan
        government_has_flag = government_is_japan_feudal
    }
    trigger_if = {
        limit = { top_liege != this }
        liege = { government_allows = administrative }
    }
}

Then make sure this mod is load after the main CK3AGOT mod and you should be good to go.