Yes, there is a variation between brands and models at a given nominal size. The 700c is a nominal size these days, that applies to any tire that fits on a '622' ERTO-size rim, from 700x23mm race tires, to 700x45mm. Confusing things slightly are that '29er' MTB tires are also 622 rims, just that the '29-inch' designation applies to those tires that are 50mm+


As to your specific fitment, I had a bike with the same Kendas on it, and found that, at least to the eye, they looked tall and narrow; I eventually replaced them with Conti Ultra Sport II's that have a much rounder profile on the bike. I may have gained a little more clearance, but I never measured them.

700x28 hits right at the wide end of 'sport' tires, and the narrow end of urban / trekking type tires. It seem like the urban / trekking / commuting tires are a little more built-up under the treads than the sport / training tires. Also, added puncture-resistant layers may contribute to a slight increase in size over nominal, as well.