After buying Instagram by Facebook company one of the first decisions of new owners was change of the timeline on Instagram for non-chronological, like it works on Facebook. All photos are segregated by using special algorithm which uses information about posts liked by us or about users which interact with us. Most of users rated these changes negatively, and after long time Instagram may change a bit when it comes to its timeline.
We can find some posts in social media that few users received information about tests of chronological order on Instagram's timeline. If it's true, then comeback to old timeline can be bull's-eye because this variant is definitely easier to understand and rules how works website will be clear. There's possibility that if all changes will work correctly, then we may receive also some changes in timeline on Facebook, but there's long way towards changing that.