Yes. During breeding season, males are about 33% larger, as they prepare to hatch the egg without eating for 2 months. That is a difference you as a human can tell.
Penguins on the other hand are evolutionairy incentivised to be able to tell the difference. Just like crows can form social groups while looking the same to humans, so can penguins, we are evolutionary incentivised to be able to tell humans apart, while they for telling other penguins apart.
I’d be cautious with saying evolutionary advantage here.
I don’t believe the “Gay Uncle hypothesis” any more than the somewhat debunked “Grandmother Hypothesis”, which aimed to explain menopause with biological altruism. Just because we could think of a way in that it might be advantageous for a species doesn’t mean it’s advantageous for an individuals fitness.
Of course, it can be still an advantage, but we’d only know with more free, uncensored research.