Yes. USB ports certainly existed on PCs prior to the iMac's release in August 1998 and announcement in May 1998. They were, however, largely unused because of a lack of mass-market USB peripherals. Keyboards and mice used PS/2 ports. Printers (and ZIP drives!) used parallel ports. More expensive peripherals (storage and scanners) used SCSI. A handful of other devices used RS-232 serial. Go back to those old PC World magazines and look for the mass-market USB peripherals available for sale and let me know what you find.
Starting with the iMac-inspired Cambrian explosion in USB peripherals and for a rather lengthy period of time measured in years afterwards, it was actually rather difficult to find USB peripherals that were not made out of translucent plastic to match iMacs.
Apple wasn't the first to market with USB (and Snell didn't claim it was), but Apple most certainly drove its mass-market adoption.