I suspect you will find an issue with regard to software drivers. Before you connected your Logitech webcam, for example, you will have installed the appropriate Windows (or Mac) drivers from the CD supplied with the webcam before physically plugging it in, or alternatively you would have relied on generic Windows/Mac plug-and-play in-built drivers.
Panasonic, on the other hand, are likely to have only installed their proprietory webcam software drivers at the manufacturing stage, meaning a Panasonic webcam will be "recognised" when plugged in, whereas a generic or other branded webcam won't. It's just another cunning example of a manufacturer forcing you to buy their (typically expensive) accessories or add-ons.
I can't see a way around this likelihood, simply because you can't "get at" the on-board Blu-ray player's software without risking screwing the whole thing up, unlike a PC where it's fairly easy to get into Windows or MacOS to make system configuration, driver and registry changes (provided of course you know what you're doing).
I shall be interested to see whether or not the WHF test team confirms this or not in due course.