Sculpt spells final ruling on 5e

While playing an evocation wizard, I had to make a ruling that did not completely sit with me. He tried to cast a fireball on top of the party and claimed due to Sculpt spells ability, nobody in the party took any damage.

I looked up the definition from rulebook which states this:

Beginning at 2nd Level, you can create pockets of relative safety within the Effects of your Evocation Spells. When you cast an Evocation spell that affects other creatures that you can see, you can choose a number of them equal to 1 + the spell’s level. The chosen creatures automatically succeed on their Saving Throws against the spell, and they take no damage if they would normally take half damage on a successful save.

I interpreted this as simply stating, sculpt spells mean creatures he chose at MOST take half-damage (due to automatically succeeding saving throw) and IF they actually succeed on their saving throws, they will take NO damage.

I felt like otherwise Evocation wizards will have absolutely no qualm in nuking their parties to take out enemies co-located with them with no penalty and with no limited resource. However wizard obviously counter-argued my approach.

Is there some official guidance somewhere I missed on this issue?