To be honest, I had never seen this function until you mentioned it. I have no idea if we can enable it on NE.SE (if we would want to) and how to do that (but we could find out, if people would find it worth investigating).
I'm not really sure how effective this measure would be. Quite a number of the closed as off topic questions don't contain that many words in the topic you could filter on. The topics are often quite generic: 'subnetting question', 'wireless router problem'. I don't see phrases like 'home network' in topics that often, it often becomes clear that someone is asking a question about home networking (or consumer grade equipment) based on the actual text in the question. So in my opinion, it would become a kludge, which would allow some topics while rejecting others.
Also, I think quite a number of people would just rephrase the topic so it will be accepted, instead of reading what's on topic in the help center, so I'm afraid the effect will not be that big.
Lastly, I think that having on hold questions visible for new visitors can function as a warning sign: they may see that questions specific topics are off topic here.
I personally don't feel the number of off topic questions has reached a problematic level at this moment. I agree that it would be nice if there were fewer, but in my opinion filtering based on words in topics is a bit too rigid right now, my preference would be to let regular voting do its work.
