I think it’s more a case of ‘horses for courses’.
I’m not sure that ‘shorter courses’ promote better learning. I think in your example you break the ‘course’ down into six ‘lessons’, and it might be that you’re saying that breaking the ‘course’ down makes for better learning.
My understanding is that when we review material over a period of time it helps retention. This might be a little different from breaking things down.
Also, if you’re doing anything in any depth, you need a good chunk of time to get into the topic. When I was doing an online Moodle course a while back I needed to dedicate Saturday mornings to doing the course work. There was no way I could have broken this down – the stop/start would have driven me round the bend.
Having said that, we produce animated videos and are loathe to have anything lasting longer that 5 minutes – but that, to us, is the nature of an explainer video – there’s a lot of information in a short time.
Less can very often be more, and more can be less.