Yes. Since the mappings expire after some time (generally it's 4 hours if I recall correctly),
it needs to be broadcast so it has a chance of reaching the target machine after the mappings are gone.
Correction: If the mappings expire, the message is broadcast anyway.
The only reason why you would need to use broadcast is in case the machine physically moved to a different port and you tried to use Magic packets to wake up the machine before the mappings expired. Sounds like that would be handy in a datacenter, but I can't say if it's actually used.
While the example I've given probably never happens, it's likely the reason why broadcast is generally chosen - it's more reliable in case of bad/outdated mappings.