Philosopher,
You asked a beautiful question from a posuk, but instead of searching for an answer, you made your own assumptions that led you to misinterpret meforshim.
Your question has already been asked and answered by the Ramban, as I have posted earlier and will post again:
ויגוע ויאסף. ומיתה לא נאמרה בו, ואמרו רבותינו יעקב אבינו לא מת, לשון רש”י. ולדעת רבותינו, הרי יעקב הזכיר מיתה בעצמו הנה אנכי מת והיה אלקים עמכם. ואולי לא ידע הוא בנפשו, או שלא רצה לתת כבוד לשמו. וכן ויראו אחי יוסף כי מת אביהם, כי להם מת הוא, או שלא ידעו הם בזה כלל.
“AND HE EXPIRED, AND WAS GATHERED TO HIS PEOPLE. But the word “death” is not mentioned in his case. Our Rabbis therefore said, “Jacob, our father, did not die.” This is the language of Rashi.
Now according to this opinion of our Rabbis, the difficulty arises: Jacob applied the term “death” to himself, as it is written, “Behold, I die, but G-d shall be with you!”
Perhaps he did not know it himself, or it may be that he did not wish to pay honor to himself.
Similarly, with respect to the verse, “And when Joseph’s brethren saw that their father was dead,” we must say that to them he was dead, or it may be that they did not at all know of this.”
In other words, the brothers “saw that there father died” because that is indeed what THEY SAW!
As Rashi write on Gemara, they buried him because TO THEM he seemed dead. But really, he was alive.
This also fits with Rashi’s pirush in Chumash on כי מת אביהם, that they FELT their father’s death because of how Yosef was treating them.
This has nothing to do with if Yaakov is truly alive, rather with the perception of Yaakov’s children.