Even something arguably well-executed and compatible with "established" style heuristics, like Grammarly, will always be dubious, as they perpetuate the myth of linguistic prescriptivism weaponized by language pedants. All of whom are annoyingly, vocally, interminably incorrect.
But this, this is just baldly idiotic.
Vale also has multiple severity levels, so disabling e.g. the "suggestion" (and maybe even "warning") level while writing live would make a lot of sense.
Not even true. They recommend against first person singular.