To Skip or Not to allow Skip?

My background is from a corporate environment, so I have two perspectives on your request for more information on this topic.

The modern theories of adult learning support allowing your learners to move about your eLearning course freely. You may often hear about the principles of adult learning. Its primary author Professor Malcolm Knowles included in his theory of andragogy that adults are autonomous and self-directed and prefer to learn using their own choices. Adult learners are not empty containers that need to be filled with knowledge and skills. They always come to learning with at least some knowledge and experience. Giving these types of learners a choice will result in an overall better experience for these people and usually better feedback on your design.

The reality is that in the end, these decisions, while influenced by you, are made by your stakeholder and, in some cases, by the government regulations that dictate compliance in your training. So, for example, your organization's legal department might say that forcing a  learner to watch the entire video before moving on to the next slide means that your organization can demonstrate that it's done everything it can to ensure compliance. In reality, you and I know this isn't true. Just because the learner sat in front of the computer screen for all six minutes of the video doesn't prove they learned anything. They may simply have been texting with their girlfriend during that time.

Compliance is ultimately the responsibility of supervisors and management. If employees are not taking their training seriously, they are likely not taking their other duties seriously. People are seldom fired for not completing their training, but they are frequently fired for not performing their duties to management's satisfaction. I don't believe it's the training department's job to weed out problem employees. All that being said, the course ultimately belongs to your organization and the stakeholders responsible for that area of learning. You can make your recommendation, but if the stakeholder wants to ensure compliance by making the learner sit in front of the computer screen for the appropriate duration of a video or other such piece of knowledge, then that's what you should do. Don't lose too much sleep over it.

There is no answer to your question really. I can only give my personal opinion. Forcing (especially adult) learners to 'watch' something is a negative approach, and not all a guarantee on more efficient learning at all, may have the opposite result. That is the case for all types of learning. In university college (live classes) some of my colleagures 'forced' students to attending all their classes. I just invited the students to remain at home if they found the class teaching not interesting, or if they didn't want to engage in it but thought they could manage to acquire the necessary skills/knowledge in another way (reason why I also provided eLearning assets). Result: I had the highest number of students attending my classes, and got spontaneous apologies in case of absences (which I didn't require at all). Students were over 18 years... 

The responsibility for personal learning should at the first place be with the learner, not with the 'teacher' or developer. 

However that means that your task as eLearning developer is to make your courses engaging and interesting enough to address the learner's needs for learning. 

BTW bit off topic: custom navigation is a better idea for other reasons than skip/no skip. It allows to have 'forced' views of course, but is less confusing for non-linear courses and you can offer more navigation control to the learner than with the default playbar and its confusing progress bar.