Referring to the question below from the link above :
Q. Is R3 a "Downstream" LSR to R4 for 10.1.1.0/24?
A. No, data flows from upstream to downstream.
When I read the answer above, I felt there is a typo (any comment) , since the traffic flows from R4 through R3 to reach its final destination 10.1.1.0/24 , hence R3 downstream router to R4, because data flows from upstream (R4) to downstream (R3) to reach its network destination (10.1.1.0/24).
Any insight ?
Please read this statement that precedes the question:
"The R4 routing table has R1 and R2 as the "next-hops" to reach 10.1.1.0/24."
As you see, R3 is therefore not consider a downstream router.
Hope this helps,