That does not mean the funds did not come from overseas. It is common that it will be passed through a local resident, by way of LLC, for the actual purchase.
SF has (had?) the highest percentage of millionaires/billionaires in the US. It is (was) arguably the richest city in the US or possibly the world. Many of the thousands of fresh millionaires that it mints yearly come from very large windfalls... which are immediately used to purchase houses in cash. At the same time, SF is building literally no new detached single family houses.
In these cases, the funds came from tech money. I made sure to check at the time so I could better understand the market. One buyer was friends with the seller, but they didn't know until receiving his formal offer. SF is a small city, especially in tech circles.