I lol at those who argue about 1x or 2x per body part

Not all bodyparts are equal.

For instance, shoulders, while a major body part, is obviously smaller than the chest or the back.

Here is what the training frequency should be like:
Shoulders 1x a week
Legs 2x a week
Back 2x a week
Chest 2x a week (however, the second session should be planned carefully as many chest exercises will involve the delts)
Arms 1x a week

Abs and calves are a little more up to personal discretion.