Interesting question. I am not really sure how to respond to it directly because I am not sure what the "extra element" is exactly. I can tell you that I do not think of myself as exceptionally philosophically mature. In fact, much of the reason I applied to graduate school is to gain that maturity. I am currently in a gap year between undergrad and (hopefully) graduate school next year. I chose to do the gap year so I could a) really polish my application and to see what life outside academia is like (which perhaps relates to your question on accumulating life experience). In this gap year, I have been constantly asking myself if I am happy where I currently am (working at a small nonprofit) or if I absolutely must return to grad school. As I am writing this, I stand with the latter option. So, perhaps it is a little presumptuous to assume you are philosophically mature (because that is part of what grad school is for) or perhaps it is something too difficult to self-assess because it is something very nuanced. Obviously, I'm aware you are qualifying the notion of philosophically mature as philosophically mature for an undergrad, which I think, ultimately, is something beyond your ability to self-assess completely. I would imagine that if you really thought about how you performed in class and the kinds of interactions you had with your profs and peers, you should be able to glean something revealing towards understanding if you are ready.
Though if you are prepared, it will surely come through in the writing sample and letters of rec.