I'm inclined to agree, except that Matrix devices work both ways. You can choose from a wide variety of commlinks, all with different Matrix attributes, just like armor. Likewise for stock operating systems. However, you can also buy the same Matrix attributes as custom hardware modules and software, in which case it follows the rating model.
For example, this ruling would allow you to buy an MCT Tactical commlink (7/7), but you could not upgrade a Singularity Battle Buddy Basic (5/5) to the same stats with hardware upgrade modules, because rating 7 modules are not allowed. (In practice, you'll run into Availability problems anyway; I'm ignoring that to focus on the one issue.)
There are ways to explain the discrepancy, like saying the components are harder to come by than the package deal, only that's not really true according to Availability. Really I think it's just an unintended consequence of a poorly-specified rule. They intended for some ratings to normally fall on a 1-6 scale, but they did a poor job of distinguishing that from the ratings with no such limit. As new products like WAR! break some of the old limits, it's hard to say when the 1-6 rule applies and when it doesn't. Are Matrix devices supposed to have a 6 cap, or should they work more like armor now?