Why is a logical linear sequence useful even though in practice instructional design components may be more concurrent
Jordan, I don't know what sort of terminology mishmash your educational course may use for this, but the essence of the answer is this: A logical linear sequence is how YOU analyse and synthesize usually a single item, factor or event at a time. Thus, you might trace "getting yourself hit by a car" backwards to "stepping into the road without looking both ways and considering the traffic hazards" and forwards to "getting taken to the hospital", etc. The ability to do this is a necessary precursor skill to solving real-world problems, which tend to present several factors at once. In your case, the students you'll be eventually instructing might have to analyse a text and write a targeted response to it. That would include components of 1) preparing to scan for information relevant to the required response 2) scanning or reading the text 3) making mental or physical note of relevant information found 4) disregarding useless information (note that you have to process it in order to decide that it should be disregarded!) 5) taking in tone, mood, etc. as required by the task, etc. Some of these may be linearly performed, but most of them are concurrently (simultaneously) performed. As a teacher, you have to be alert to students who haven't acquired some of these specific skill components, analyse which skills those are, and schedule practice on those skills specifically for those students -- without boring the students who have already acquired them!
Fortunately, you have techniques for this, such as open-ended, multi-leveled assignments, and so on.