i can live with the idea of the pensive making seen what is unseen- like it is described as a method to step away from all the emotions and the turmoil-as torino states before me- so i can also agree that maybe the magic saw and the pensive makes it seen - because we know we see way more than we realise, and we also hear more than we know, but our brains filters out what we deem important, so maybe we can say like the magic expands the field of awareness and the magic of the pensive enhances that and show all that the wizard missed...

but i agree with you that the legilimens is a cheap way to show the reader some backstory which other way wouldnt have been there- because how?
all the ppl were so busy with telling harry how awesome his father was?

i can live with it and since as a writer i bend the canon as much as i like and do what i want i dont really concern myself that much with cannon- but the question itself is rather interesting