ΔE 25.4, loose: different enough that you should pick on purpose. Flat Yellow is noticeably darker, much more muted, warmer than Battle of Yellow Tavern.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Flat Yellow is noticeably darker, much more muted, warmer than Battle of Yellow Tavern.
The same difference applies the other way round: Battle of Yellow Tavern is noticeably lighter, much more saturated, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Battle of Yellow Tavern on the colour wheel See Flat Yellow on the colour wheel
All matches: Battle of Yellow Tavern equivalents · Flat Yellow equivalents