Unfortunately it is true. SWA does not say it is OK to save seats or that it is not OK to save seats. They generally will not stop passengers from putting bags, books, coats, arms, legs, etc. in an empty seat to save it for someone, but they also won't back up the saver if someone tries to take a seat that is not occupied by an entire person. Different FAs will have different approaches, however, so you may find some who are actively discouraging seat saving and others who are more tolerant of the practice. The only thing that might guarantee their involvement is some sort of confrontation; which their lack of a definitive policy would seem to make more likely.
I will say that if the saving is holding up the boarding process to any significant degree that it is much more likely that the FAs will take some action to address the situation. Again, it won't necessarily be consistent in terms of how they address it. Some might encourage passengers to grab any seat without a person in it and some might just tell people to keep heading to the back of the plan.