Generally yes, but cases are variable

Generally, yes. There is a reason why either of delayed debuts (virginity) or committed relationships (early courtship and marriage) are the most widespread models of sexual development in girls.

But cases vary.

And the knowledge that girls are more likely to interpret early sex with a negative narrative is necessary for the GLer.

Hypothetically, in a society where the complications arising from legal penalties and their avoidance are zero... the GLer still has to have a committed relationship with the girl. That relationship reassures the girl in her future narratives against feeling used or shortchanged (which, you shall notice, is a common theme in Ethan). My ideal is that this is a long term, potentially lifelong, relationship. But that isn't even strictly necessary; as long as any breakup as she grows older comes from her, and as long as GLer and (ex) girl remain friends, then the communication channels never close, and the reality of a continuing friendship disproves any hypothesis of "use and dispose" that she may otherwise entertain. (Of course, this is the same in the sort of incestuous relationships you personally seek for).

But if you just want to add a new warm body to your count and you don't intend to see her anymore when she grows hair and bewbs, which is the assumption of the free-for-all position, then yes, don't act surprized that most (ex) girls will assign that experience a negative narrative. (Even as most boys wouldn't, or at least a higher percentage wouldn't).