The Torah gives us B'nos Tzlofchad's claim as to why they (in place of their father) should inherit their portion in the land when they entered Eretz Yisrael. They are right, and Moshe learns after speaking to Hashem that they will inherit the land. Now, the Halachah wasn't changed because of their complaint or the perceived unfairness. After all, HKBH is perfect and always fair. Rather, He waited until now to teach this Halachah because He wanted to give B'nos Tzlofchad the opportunity to show how much they loved Eretz Yisrael and ask for it themselves, and therefore they would be Zochos to have 2 Parshiyos in the Torah written because of them.
What intrigued me today was part of their claim. They said that there father had not died B'Adas Korach and hadn't complained. Rather, he died for his own sin (which one opinion in the Gemara (maybe R' Akiva?) learns to mean that he was the Mekoshesh). Now, what was the point of the Torah telling this? It is understandable that B'nos Tzlofchad said it. After all, they would make every possible argument to earn themselves their portion. But in the end of the day, that fact is irrelevant. A daughter without brothers inherits no matter what. Even if Tzlofchad had been part of Adas Korach they still would have received the land. So why does the Torah add that line?
I also don't think the line is there just to tell us who the Mekoshesh was. After all, just knowing his name doesn't add anything (especially because, if I recall correctly, another opinion in the Gemara attacks that opinion as Lashon Harah). I had a thought that maybe it's even more respect for how much they loved Eretz Yisrael. Not only did the Torah record that they asked for it, but it even records an extraneous part of their conversation (from which we could also possibly learn who the Mekoshesh was).