The most important thing to take note of in that article is that KC ran a two gap front, which is being phased out of the NFL in favor of one gap attacking fronts.
Many fans still think about 3-4 defensive scheme using outdated techniques and responsibilities. Hell, even "expert" sports analysts often make that mistake.
The concepts most are familiar with, like "Five Technique" and "Zero Technique", are not strict standards anymore. The 49ers defense rarely lines up that way.
The biggest issue I've noticed when fans are talking about defensive "needs" is the enigmatic "True" nose tackle. This concept is pure myth and is a term that fans use because they are thinking in terms of two gap 3-4 schemes. It's something that even the most intelligent and educated of fans continue to preach.
Again, the 49ers defensive scheme utilizes one gap principles. Here is an article that may help in understanding the difference... just ignore some of the players they use as examples: