um yes thats right!
The engine rocking is taken up by the soft rubber engine mounts, dumping ya clutch will put strain on the clutch, crank, box, dif etc but nothing to do with the block.
your on about the piston slap putting sideways pressure on the block but this is why ford changed the 4x4 pistons with off set gudgion pins to almost eliminate this problem.
revving the nuts off it is just putting stress on the internals such as crank, rods, and bolts.
The pistons just damage the block by general friction wear but they don’t exert any great force onto it.