There may be any number of reasons someone would want to do this, karma accumulation being only one of them. Product launches, Kickstarter campaigns, advice being sought or offered, etc., are equally valid and perhaps more likely motives.
Furthermore, I don't think it's fair to infer that the author advocates "gaming the system," or at least not the exclusion of writing good content. Rather, I inferred that he took writing good content as a given, and focused on the oft-pondered problem of how to break out that good content in a crowded news market.
All of that being said, your point #1 is extremely important. People should focus on quality first. It may be possible to game some spammy content to the top of the pile. Eventually, though, this strategy will do the poster more harm than good, whatever his intentions may be.
Just kidding. But to contribute something to the discussion: I was just recently wondering when the best time to publish a "Show HN" would be. In that case, your content is what it is. The time factor would definitely be important then to help you get the "early exposure" that you'd need to even arrive on the front page in the first place.
Since there is a degree of luck involved in getting to the front page, I hypothesize that you can leverage the law of large numbers to maximize your chances of getting karma by also submitting HN-targeted content regularly/frequently.
thanks
1. By writing original content that the HN audience is likely to like
2. By submitting that content at the right time
#2 is useful to know and anyone can do an analysis and figure the best time. I did it myself some time ago and came to my own conclusion about the best time (which is similar to the OP). But #1 is far more important than gaming the system. Focus on writing good stuff.