This is basically what any discussion on dark patterns i have ever seen devolves into: "a service i use has an interaction i don't like. it's a dark pattern." the whole term is basically a meaningless buzzword now.

requiring an email address to access a service is no more of a dark pattern than requiring payment to access a service. they're taking something of value in exchange for providing something of value. it's only a "dark pattern" if they trick you into providing your email address somehow.