Meta's has been listening to some concerns after all especially now after some pressure.
These changes very well could help parents moderate their teens. Meta's head of product says these changes address particular 3 concerns in an Npr interview.
Will this be the end of the complaints and concerns geared towards Instagram, probably not.
I think it would be naive to think that they don't know this already. Not to say that I think you're making that argument, but that I think the losses are calculated against the benefit of the appearance of care that this move affords them. Sure, these new restrictions and tooling means that some parents will be more willing to allow their teens to engage with the platform, but there's no way that will outweigh the active user reduction in the targeted age range.
The real benefit is looking like they're doing stuff in a positive direction in the context of minors. I'm definitely expecting them to point at this move (and its voluntary nature) as an argument against future regulation proposals. Especially the part where they're ostensibly putting that control in parents' hands.