"Will Unknown County Categories be set up for other states as well?"
Well, speaking as one new member of the Categorization project (and not for any other members of it!), and also as the new Maryland subproject person in the U. S. History project, I personally don't plan to set up an unknown county category in Maryland. At the moment.
One of the plusses of WikiTree is that we have a lot of different people with different interests and different ways of doing things, and they all contribute. Today, I personally don't see a lot of value in categorizing people by state or county; perhaps tomorrow I will. (It's a non-issue for Maryland because someone else has already set up county categories.) I do see the value of categorizing people by the ship they arrived on, the land grant they lived on, or the very early colonial county they were associated with. Two people associated with Lower Norfolk County, Virginia, in the early 1600s probably had some connection with each other, and that is important for genealogy. But aside from that, I won't be going out of my way to spend my time categorizing Maryland people by state or county. If I'm working on a profile and I see it is already categorized by state, but the county is known, I'll probably recategorize it by county because it IS important to categorize people by the lowest possible level.
In a sense, profiles that are linked to the Maryland state category rather than a county category, ALREADY constitute a "to do" list; they don't need to have an interim move to an "unknown county" list from which they'll ultimately be moved to a county list when known. But I really think we need to honor people doing things differently in ways that work for them that don't massively get in the way of others; Liz has taken on Virginia responsibilities and if an "unknown county" category helps her and others working with her on Virginia, more power to them! And if someone working on another state feels that an "unknown county" category will be a helpful way to spend their time, great. I don't see a problem with it. And if I find myself working on a Virginia profile, I'll be a team player and do what the others are doing!
One issue that Liz is responding to by not wanting people profiles on the state page is that WikiTree puts people profiles and space/topic profiles together. So at the bottom of your state category page you've got an alphabetical list that includes Jackson, Abraham; Jones, Henry, and Jordan River Redevelopment, all in the same list. It would be nice if they could be two separate lists; you do want some space/topic profiles linked to a state category, and having a number of personal profiles interspersed can make spotting things difficult. But when you move the people profiles to the county categories, where you might also want to link some space profiles, you've just moved that problem to another level!