Obviously the title is just wrong - the die is not "cast". The die is produced as a monocrystalline silicon ingot using a seed crystal, then sliced into wafers and fabricated via photolithography. A truly "cast" ingot would never work.
In the case of t article, the Rubicon has been crossed, and also features "cast" into the silicon can't be fixed (most of the time). But you're right, they aren't actually cast.
The ordinary view would be that "cast" refers generally to the making or composition of anything by any means. Compare a few senses from Merriam-Webster:
[v.t.] 3(a) to dispose or arrange into parts or into a suitable form or order - I shall cast what I have to say under two principal heads.
[n.] 2(a) the form in which a thing is constructed
[n.] 10(a) shape; appearance - the delicate cast of her features