I have had many fills with a group of smaller contracts - example 10 gets filled 5 3 2 11. I also recently looked at some time and sales data and was surprised by all the 1's and 2's and 3's.
Who are doing all these little contracts? What are the motives?
I'm finding it a bit difficult to understand your queries.
I regularly trade 1 or 2 option contracts at a time, and have for many years. I am/was unaware of any moral or legal requirement to trade a larger number of contracts for each trade.
Regarding your specific example of GS, at a share price of $209.37, a one contract trade represents a stock position on exercise/assignment of over $20,000 - which isn't a small amount of money.