The people in charge of Instagram may have used more and more of Facebook's tools, looked at better analytics, tweaked, used lessons learned from Facebook, etc.
While I agree it's unlikely that Facebook left them entirely alone I don't think it's necessarily fair to say they meddled just because things have changed. Nothing stays the same especially in the tech industry.
Contrasting this with Oculus; I think IG was given a lot less hands on MGMT.
[1] That one is a bit of a stretch, but you can already "follow people" and they market themselves as a social network, so...
Even companies like banks are using individual Next Best Action models to determine what marketing decision is right specifically for you rather than something generic to your demographic.
Having said that, I don't think it's "Facebook" doing this. This has probably been Instagram's approach to product from day one.