As of my understanding, Fill factor of 80 implies that 20 percentage of each leaf-level page will be empty to enable future growth. I can't correlate how fill factor of 0 and 100 can be the same! Am I missing something?
It is legacy from SQL Server 2000
0 and 100 were different back then
Since SQL Server 2005, both mean "fill all pages including all b-tree index levels"
Quotes from BOL (My bold)
What I can't find is something to show this explicitly in "behaviour changes"