The fact that this works reflects that fact Safari hasn't implemented the IDN standard fully, and neither has the .LA domain registry. Section 4.2.2 of RFC 5891 forbids the Emoji codepoints from being encoded in a valid IDN string.
Edit: Nevermind, the rules used to create the chart are designed to disallow symbols. It gives an explanation of the rule but not the reason it was set.
These rules identify characters commonly used in mnemonics and often
informally described as "language characters". In general, only code
points assigned to this category are suitable for use in IDN.