I bet forcefully unsetting it bumps their usage metrics for the new site though.
Mine never unsets, unless i accidentally click that damn button. I often mistake it for the reddit homepage link.
I set a custom uBlock filter to be rid of it.
It has never unset for me.
I've created a Firefox extension that allows you to change Reddit subdomains easily (without having to type). Unfortunately because of covid, the queue for approval can days or weeks right now.