It is the same as any other course I have taught. The instructor has to break the material into chunks and provide an opportunity to get feedback from the participants. This feedback lets the instructor know that the information is being received and understood.
When you are able to see the class, and the class size is small, it is possible to get some feedback via visual cues. When you can't easily watch the eyes and body language of the students you have to allow the students to provide that feedback by other means: asking questions, completing exercises, answering questions.
A training class, like any other meeting must have goals. When the class is completed what are the goals of the class designer, the instructor, the students; and how can the those goals be measured?
If the instructor drones on for 20-30 minutes with zero feedback it is clear that the instructors goal was to plow though the material with no regard for making sure the student understood the material. It is unclear if that matched the goal of the course designer. And in the case of the students it may or may not have met their goals.
A few months ago I was a participant in a series of training classes via a web connection. The instructor talked in one continuous sentence for the entire 30 minutes. They immediately ended the class with the phrase see everybody next week. They ignored all the questions that students had written via the interface. The slides weren't provided until several day later, and it was easy to see that they had just read the words on the slides. The next week it was clear that that was how the class was going to be run. The students got credit for being logged in during the class, and the instructor didn't even have to have any domain knowledge. Easiest class ever, but zero information retained.