It's absolutely new. No HTML5 features were restricted to secure origins only pre-LE. Today, many are. Google was able to push these requirements in large part due to Let's Encrypt's success making secure origins ubiquitous.
This isn't to say that these two things are unrelated: Mozilla obviously knew about Let's Encrypt and we considered it an important complement for this kind of policy, and at least some people at Chrome knew about LE, though I'm not sure how it played into their thinking. However, it's not as simple as "LE happened and then people started pushing for secure origins for new features".
A lot of thd new APIs have to do with accessing hardware. Camera, Microphone, Serial ports (currently experimental) etc.
Given how easy a MITM attack to injection JavaScript or HTML into insecure pages is, a world where insecure pages had access to hardware makes that hardware very vulnerable.
Even though all you'd be doing is reading some random blog etc.
To those who still think serving HTTP is some sort of principled stand, just be aware that injecting malware onto your page at delivery time is pretty trivial. Quite honestly, and I mean this in a constructive way, it doesn't signal "principles" it signals "incompetence".
