[mattfranklin]

I had an engine with standard rod bearings on a 0.010 under crank. It's pitch was a thud thud thud like a rod bearing, but at a really fast repeat rate, like rocker noise.

Here's how I diagnosed it:
When I had 10W-30 in it, it was always thud thud thud. When I put 15W-40 DELO oil in it AND it was cold, it was quiet. When it warmed up, the thud thud thud noise started again.

It wasn't until I had the engine out for a rebuild that I was able to confirm it.
As you observed, they all wiggle sideways, but mine also wiggled in the direction of rotation. Once I pulled the caps, miked the rod journals, and read the STD on the backs of the bearing shells, I knew what was going on.

I was amused and annoyed that someone would do that.
Buy, hey, we all have to learn somewhere.
Maybe it was some guy's first motor.