Would This Be Considered A Coin Spill?

My guess, since the majority of the coins you have found have been in the right side or your lawn (if facing the house), is that coins were scattered when previous residents reached into their pockets (or purse) with their right hand to retrieve their keys when walking up the sidewalk. When they pulled the keys out they also may have snagged a coin or two that headed towards the right side of the yard. So, it is just the occasional lost coin and not a spill.

(Most people are right handed, too!)

When I was a teen back in the '70's, I threw handfuls of copper cents into my front yard.

Yes for a purpose.