How can advanced spark lever damage rod bearings?

[Texas Tom]

The September/October RESTORER has an article titled "Ignition Timing Dwell & Backlash." Very interesting.

At article's conclusion, author states: "All the way down on the spark lever would be too far advanced and result in damage to the rod bearings."

Questions:
1. Why would Henry design spark lever movement range that included a position that would damage bearings?

2. What -- specifically -- would the damage be?