Why does recommended door rough opening height add 2-1/2" to door height?
I might quibble about floor thickness (3/4 for wood strip flooring), jamb thickness (closer to 5/8) and you're missing a gap between jamb and header (1/2 to 3/4), so I would add 1/4 +1/4 +1/2 to 3/4 for a 2 1/2 to 2 3/4 RO