"Can category specific judgement be used against us in court, to keep liability low ?"

Changing your word "judgement" to "argument", the answer is probably, but the better answer is that it will depend.

This was the strategy HTC used because the category had very few companies in it, and because those few that we signed were receiving low Royalty rates due to us still being in the early mover tiers.

Apple was shifted over to the Mobile Phones category by them because it's Royalty rate to Royalty base was so incredibly out of wack that it pulled the already low early mover royalty rates down to almost nothing.

It was an excellent logical argument, and it pretty much worked for them in the amount Awarded.