Do these guidelines need to be followed on other sorts of recommendation questions other than system recommendations?
No. Our game recommendation guidelines never really got genericised. It is not universal. It applies spottily to some things other than the recommendation of actual games, but not to all recommendations.
What applies to all recommendation questions is good subjective guidelines. Our game-rec rules just translate these with some extra specifics. The good subjective guidelines are the one that carry the famous Back It Up principle, i.e. our iron-clad rule you must be able to say you've seen it done or can back yourself up with a conclusive reference.
We've had some discussion on the generic-ness of our game rec rules. Here's the results:
- http://meta.rpg.stackexchange.com/q/2711/1204 (December 2012). The most conclusive answer in here opposes a genericised tag. That's the most conclusive answer we have here, it's tied for the second most upvoted answer we have in the meta game-rec tag.
- http://meta.rpg.stackexchange.com/q/3251/1204 (December 2013) has an assertion game-rec is for published adventures too. That's one of the areas we've also applied our game-rec rules. It has only a modicum of support.
- http://meta.rpg.stackexchange.com/q/3335/1204 (February 2014), an assertion that we should not genericise the game-rec tag, and in fact focus it back on recommending actual games, received some decent support and very little response otherwise.
- http://meta.rpg.stackexchange.com/q/5399/1204 (March 2015) asserted that the game-rec apply. Speaking as the author, I don't really know what I was thinking in writing this - I think I was trying to bring some order, but none was really needed. All I needed to do was mention the GSBS stuff which applies anyway, not our heavyweight game-rec rules. To this day no question in tool-recommendation has received that blue game recommendation rules notice.
No strong support for genericising game-rec has ever been demonstrated by the community nor have we taken action accordingly. We've extended it to modules and expansion content but that's about it. The game-rec rules were written for recommendations of games and still have the according language. We're not headless though, the game-rec rules are just an implementation of the important bits we still adhere to anyway: back it up, don't be too broad, etc.