[Docs] Follower Reads documentation should be changed wrt expected behaviour

[lizayugabyte]

Description

Relates to #14675

A change is required in https://docs.yugabyte.com/preview/explore/ysql-language-features/going-beyond-sql/follower-reads-ysql/#expected-behavior based on the following slack exchange:

Mikhail Bautin
Why was "read happens from closest follower" replaced with "read happens from closest tablet" for yb_read_from_followers? Each row resides in a particular tablet and we can't choose to read it from this tablet or that tablet based on which is closer. Each tablet has multiple replicas, and with yb_read_from_followers enabled, we allow reading from the closest follower of the tablet rather than always reading from the leader. So, this particular change is actually wrong.

Liza Rekadze
There was doc ticket asking to replace follower by tablet in this document. The commit belongs to the PR addressing this ticket: #14675
Perhaps Marko Rajcevic could clarify.

Marko Rajcevic
My understanding was that even if we read from the leader we read from Now()-yb_follower_read_staleness_ms. So regardless if it was the leader or a follower you are going to potentially have some staleness. That was the intent of the change, it was meant to avoid confusion with users assuming that only followers will be read from Now()-yb_follower_read_staleness_ms. Would you recommend to keep it as "read happens from closest follower" or a different phrase all together?

Mikhail Bautin
It is correct that the read could still be done from the leader. But it never happens from a different tablet.
Suggestion:
"read happens from the closest replica of the tablet, which could be leader or follower" (edited)

Marko Rajcevic
Thanks, good catch.
Can we make the edits above?