Q:

What is the purpose of these two diamonds in Celeste chapter 9 (Farewell)?

In the Reconciliation sub-chapter of the DLC chapter (Farewell), there are two refill diamonds (one single diamond, one double diamond) hovering at the top of the screen. As far as I can tell, these serve no purpose. It's very difficult to reach them, and the bird throws you right past them. 
Given the presence of multiple hidden branching paths in this level, I'm suspicious. Are these really just superfluous diamonds, uncharacteristically forgotten by the developer, or are they significant?

A:

Those diamonds are part of an alternative route. You can use the route, but you have to waste some time before jumping towards the diamonds (I did it by dashing up):

To get there a bit earlier and in phase, you'd have to also use the other alternatives:

This route is faster than using the bird, so it would be preferable for a speedrunner.
I died way more than I'd like to admit while trying and routing through that. I didn't actually count my deaths though.

