You don't really have to let it cool if you don't want to....Think about this, you are dropping 2 cups of hot liquid through an air space into a bucket, that hopefully has some starsan or other sanitizer liquid hopefully in the bottom, that alone is going to cool the boiling liquid down, and mere seconds behind that you have 5 gallons of liquid colliding with it, it's going to go from near boiling to beer temp, really really fast.
And it's not going to hurt your beer or yeast to come in contact with the boiling liquid. Again it is such a tiny volume in regards to the greater volume of beer it is coming in contact with.
You can cool it if you want, I have that factored into my bottling process (as illustrated in my thread) somewhat, where it sits about 5-10 minutes on the stove or counter before I transfer it to the bottling bucket.
But it's not necessary. Like so much else in brewing, it's purely your preference how you want to do it.
I've done it both ways, and the beers carb up fine. So it really doesn't affect the process one bit.
SO do what works for you.