At the station where I worked that meant the underground tank was almost empty. We had two tanks for regular and would throw a tank selector switch in the station house when we saw that happening, and the fuel dispensing speed right back up.I had this happen couple weeks ago. I was only one using pumps. Took 10+ minutes to fill up.. Went in and ask clerk. Aware of it, didn’t know why, called manager, supposedly someone coming to check it out.
I don't keep pumping if it is slow like that. I think the air slurping causes disturbance in the underground that will stir up sediment. Plus all tanks have some water in the bottom.