ΔE 29.0, loose: different enough that you should pick on purpose. White Scar is noticeably lighter than Glass Moon Light.
Can I use White Scar instead of Glass Moon Light?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). White Scar is noticeably lighter than Glass Moon Light.
Can I use Glass Moon Light instead of White Scar?
The same difference applies the other way round: Glass Moon Light is noticeably darker.
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.