Found these on CL. I've never seen wheels with multiple configurations/drillings such as these. Is this for real?

Is this for real?

Most certainly. Not overly common, but I've seen it before. These days, those are two of the most common bolt patterns, so by combining them on one part number give the most coverage for the least inventory. Simply economics.

No structural issues? I assumed you cover the holes with a center cap...

Seems like the metal between the 2 adjacent bolt holes would be

prone to break under hard cornering, no?

Or they'd break when some tire jockey with an overactive touch with his impact wrench tightened them. I wouldn't put wheels with that setup on any vehicle that I owned.

Don't get me wrong guys, I never claimed it was a good idea. But it's not totally unheard of, either. I've seen several examples of this in my 2+ decades in wheels and tires. And while I personally don't think it can be as strong, frankly I can't recall ever seeing a wheel like that broken in the center, either. So it might not be as bad as it seems.