If using a surface segment, which city is considered the point of stopover: the city of arrival or departure? Makes a difference in terms of being able to depart from one of those cities a second time.

The following assume SYD to LAX, then surface, then SFO onwards. So, is LAX or SFO considered the stopover city when that surface segment is employed?

For example, if LA is considered the stopover city, then one could/should be able to do:
SYD-LAX-surface-SFO-JFK-SFO-LHR-...

If SF is considered the stopover city, then one could/should be able to do:
SYD-LAX-surface-SFO-JFK-LAX-LHR-...