There's not a lot that is done with switch cosmetics -- they tend to look similar. Moreover, sometimes switches that are identical on the inside look different from the outside. So the counter-argument would be that Cisco could very well decide to source the boxes from the same manufacturer for Cisco and Linksys, yet put in very different contents. One box is about as good as another, and doesn't determine the quality of the contents at all. Because of this, the look and details of the external cosmetics is not at all conclusive.
However, in this case, if you look at the cheapest such Cisco switches (2960G line) and the Linksys ones, you'll find significant differences in the layout and configuration of ports, etc., which indicates that the switches are at least somewhat different on the inside. Moreover, the Cisco has significantly more buffer memory -- this alone puts them in different categories.
Finally, it's known that Cisco and Linksys are not closely integrated internally -- they operate different design and engineering teams.
I'm calling "myth" on this one.