/playsound command doesn't work with selectors not resolving to exactly one entity

When executing the command "/playsound minecraft:entity.player.burp player @a", I get the response "This player cannot be found"
The command works fine with @p or if you use a real players name, but just not with @a

The same thing happens both when the command is executed by a player or is executed by a command block.
And it happens with every <source>, not just "player".