Flange needed on slip on tub spout?

Just put a new diverter spout in for one of my tubs. It had a slip on spout, caulked to the tile, over a hole in the tile and backer through which the 1/2" copper pipe passed. The hole was bigger than the copper pipe and smaller than the spout.

I reinstalled the same way. Put the slip on spout on, verified not leaking, caulked around the spout.

Now I'm wondering if I should have put on and caulked a flange behind the spout. Seems like a good idea in case there is any leaking out the back of the spout. Is this common, a "good idea", considered essential?