Instead of thinking of covering in terms of material, think of it in terms of students.
Suppose you are teaching only one student, then you (hopefully) know how to listen to and watch the student and adapt the lessons to maximize his or her learning. In this case, if someone asked you what you covered, you’d define it in terms of what you know the student learned. If there was some topic that you discussed, but you know the student just didn’t get it, you probably wouldn’t claim that it was covered. This is because if in the future this student is asked about some topic you claimed to have covered, and acts like he or she had never seen it, then you’d just look foolish.
Now, suppose you are teaching 30+ students, and are using the best teaching techniques you have to maximize the learning. If someone asked you what you covered, you’d define it by what topics you covered, knowing full well that not every student got each and every topic. If later a student is shown to not know something you covered, you always have the excuse that ‘you did it in class’ or something similar. Being able to hide behind the ‘covered compact’ can mean that a teacher doesn’t really have to work at developing or improving his or her teaching so as to increase the quantity and quality of the learning that happens in his or her class.
As a new thought, consider the class as a collection of individuals, each having a profile of effective learning strategies. For example, one student (or group of students) might learn best through direct instruction, which another might prefer hands-on activities. Now we can talk about what happened in a class over a semester by the topics, the variety of teaching methodologies that were used to teach each topic, and the results of the assessments, with the expectation that all the students’ learning strategies were covered for each topic. We might even want to report our results in terms of this breakdown, e.g. for Topic X, all students were covered, but for Topic Y, mostly students that learn through reading got the material, etc. Or we might be able to list which topics we taught by what means. Then when a student shows up in another class, the description of what they should know can be more detailed, and any weaknesses in his or her preparation can be traced back to the type of teaching done, not just whether or not it was ‘covered’.
This perspective brings up some new issues. For example, if one teaching style is highly effective for a majority of the class, but is totally ineffective for the rest of the class, is it proper to only use that style? What if the effective style for the rest of the class is bad for the majority, so that by any type of mixing of the two styles, the overall results (in total) are lower? Related to this is how much should students be expected to adapt to the teaching style(s) in a class? I don’t think there is an easy answer. I’d probably err on the side of trying to reach all in some way rather than maximizing the overall result. But I also think it is part of our job to help students learn to adapt, and so, at some point, I’d probably expect more of students in terms of being able to learn from a limited variety of styles.