The cutoff for baggage check in on a freestanding international departure from SFO is already just 1 hour,
And even that is only due to TSA/DHS requirements for check-in on international flights. For domestic flights at SFO it's 45 minutes.
Of course, the difference with transferring is that they need to get the bags off the inbound plane first, but as you've said, 60 minutes is plenty presuming the inbound isn't too late.