If the water has chlorine, and if the filter is an activated charcoal filter, then putting it in front of the softener to remove chlorine first makes sense. Chlorine is not so good for the resin. I definitely would put a backwashing iron, and/or manganese filter first on a well or city water to leave the softener with less to deal with. So with that in mind what you you understood the person to say is wrong.
If it is a sediment filter, putting the filter after the softener could catch the rare broken resin bead fragment If it is a 0.5 micron filter the filter after the softener would not clog as quickly. I would think that a 50 micron filter or a spin sediment filter would be before the softener. I don't know if a softener should have to face well water without a sediment filter before the softener. On the other hand, having the softener deal with sediment gives less for a cartridge sediment filter to deal with. So with a sediment filter, I am not sure.
An RO filter should be after the softener.
There may be some kind of filter where you would change the location based on city or well water.