benignuman:
This was presented by the OP as a halachic statement, and you cannot simply dismiss that as “not meant to be amen literally”.
charlie:
“Rambam didn’t include that as an ikkar of faith. Neither did R’Hasdai Crescas. Nor did R’Yosef Albo. It appears in none of the lists of 613 mitzvot. Does an Acharon have the power to change halachah by adding an ikkar?”
No, he doesn’t. Which is why if R’ Elyashiv did indeed issue such a psak, he probably either felt that this should either fall into one of the categories brought down by the Rambam, or that believing in evolution was merely contrary to the Torah, and that it would be considered like a ger was not completely mekabel the Torah.