In SQL server, why is N'🙂' equal to N''?

Question

I don't understand why the following returns 'Equal':

SELECT IIF(N'✅' COLLATE Latin1_General_100_CI_AI_SC = N'' COLLATE Latin1_General_100_CI_AI_SC, 'Equal', 'NotEqual')

returns Equal

I am aware that sql server ignores trailing spaces when comparing strings however I don't understand this result.

Even more bizarre, if I use a different emoji, the result is 'NotEqual':

SELECT IIF(N'🙂' COLLATE Latin1_General_100_CI_AI_SC = N'' COLLATE Latin1_General_100_CI_AI_SC, 'Equal', 'NotEqual')

returns NotEqual

Edit: I'm aware of https://stackoverflow.com/questions/47551528/sql-query-where-column-returning-emoji-characters-and and the fact that the behavior is expected on older, non-100 collations. However I am using a 100 collation here.