That hub doesn't look like it has clues that sometimes indicate issues. On some failures, it's apparent that there are issues, such as oxidation or the beginning of shallow cracks. The only mark near the break in the pic seems to be a little dark spot from oxidation. Can't see if the other 2 areas of the break shows any type of older indicators (like area in the cracked area that is already oxidized that shows that it pre-existed).

Have seen some older hubs that seem to be made of lower quality aluminum. Also have seen some lower-end Shimano ones that suffered failure.

Many of the newer hubs are investment cast and could use different alloys from older forged ones. FYI, Shimano has a list of front hubs that are recommended for radial lacing, these seems to be just higher end presumably forged construction.

Really can't tell from the pics what caused the failure. It could just be age and the exposure to chemicals or repeated stress. Don't know enough about aluminum alloys to understand how it may 'age'.