WebGL does have to do some validation, but most implementations are built on top of ANGLE, which for the most part is _NOT_ an emulator. It does have slow paths for things that exist in WebGL such as the TRIANGLE_FAN drawing mode that don't exist in D3D11. For an interesting read, might I sugguest: https://books.google.com/books?id=6crECQAAQBAJ&lpg=PP1&pg=PA...
IMHO, export of 3D models to HTML5 is superb technology and will be used everywhere. For example, clothes shop can use it to display clothes on model of customer, in dynamic (walking, dancing, running, etc.). Car shop can use it to provide virtual test drive. Constructions shop can use it to let customer practice with tools and materials. Anybody willing to start SaaS startup in that area? I am working for outsource firm, so I cannot start a software startup, because I will be fired immediately and I have not enough savings, but I can be hired. I have more than 25 years of experience in programming and more than 30 of successfully finished projects (and 2 failed), I participated in few startups (e.g. Bazarvoice), I saw my code spread, e.g. in BashFAQ, etc.