When we talk about training, we need to think about the whole picture! So when we think about fatigue and what workouts cause the most amount of fatigue, we need to think about how many muscles are activated and to what extent during each exercise. For example, when we are training biceps by doing a standing curl, you could possibly argue all muscles in the body are activated, but not to an extent that is very high, outside of the biceps themselves.
However, when we squat we can also say nearly all muscles are activated and this activation is much much higher than that of the curl example. So if more muscles are activated to higher levels, we can assume more energy is being burned, metabolites are higher and systemic fatigue is greater. So when we think about fatigue, we need to think about how the body functions as a whole. Not all exercises are made equal and not all exercises influence the body the same, especially in terms of recovery demands.
Typically, the recommendation is that the more systemic fatigue a workout creates, the greater the demands are for recovery, especially post-workout protein intake.