Yes, the call to the ApplyEffectToSelf() function comes after PreActivate(), when the skill is already active and I’m checking the requirements with ActivationOwnedTags, but they’re not activating yet. And this applies to all other abilities that apply a requirement tag effect. 
I also checked the tags applied to the character’s AbilitySystemComponent and they are also being applied, as well as the SpecHandle that is used to apply the GameplayEffect.