And the vast majority of the time, we just pretend it's a weird syntax if-statement.
The practical importance is that we use the same tools to search for implementers and senders of #ifTrue: as we use to search for implementers and senders of any other method. (We use the same pencil to sketch that we use to write.)
By contrast, Smalltalk is so deeply object-oriented that it doesn't technically even have an if statement, just instance methods in the boolean class.