I want to add, this was an existing ruling, they just clarified the rule. Every article it seems is using each-others clickbait titles(the linked article even references it in the edit).
The change that they made was that they added a dedicated section to the developer guidelines, where before they only had it on their pricing page.
This rule has been in effect for 5 years now according to steamdb.
Whatever happens on mobile has ended up being adopted onto traditional gaming platforms down the line. My first encounter with stuff like IAPs was on mobile and lot of people's first introduction to gaming these days is mobile games, so next generation will be more open to it.