WebM w/ Alpha (Transparent) background Not working in Premiere/After Effects

[#1]

I have noticed that my Transparent WebMs are no longer being viewed with an Alpha Layer in Premiere and After Effects. These files definitely have an Alpha layer in them and when I upload them to the web they display accordingly. When I import them into a project in Premiere or AE, they have a black background.  I downgraded several versions in Premiere and they are still showing up without Transparent Backgrounds, but I am fairly certain this worked in the not too distant past.  

When I right click on these WEBM files in the project pane and go to Properties, it shows they do not have an alpha channel, but they 100% do.  

Why does Premiere (and AE) not recognize the Alpha Channel in these WebMs and how can I fix it so that I can work with WebM files (which are 10x smaller in file size) instead of massive MOV files?

[#2]

premiere needs external webm plugin for support