If you missed it before, I'll say it again. The biggest benefit to a cast crankcase is a lower manufacturing cost if your volume of parts can pay for the dies.

The ZDZ-40 crankcase (front) sells for $27. Shocking, but true. Also a casting allows you some design freedom not allowed by machining. There are certain shapes and dimensions that cannot be machined because you simply cannot get a cutting tool in position to remove the metal. ZDZ, 3W, MacMinarelli, and Zenoah are cast. Michael, you aren't going to get rid of your 3W-150 SS and trade it in for a DA are you, just because the DA has a wrought alloy crankcase?

The Taurus crankcase could be made out of platinum plated ferro-impervium for all I care. The engine still won't run any better or longer than the inexpensive ZDZ. A crankcase is not a bank vault and does not need to survive atomic bomb blasts. It needs to keep the bearings in alignment and to keep the air out - that's all.

As for 6061-T6 aluminum alloy. They chose this alloy because it's relatively easy to machine, not because it's the highest strength aluminum alloy available (and it isn't even close). Gee, they were lowering their production costs, what a surprise.