https://unity.com/pricing-updates
Does the Unity Runtime Fee apply to web and streaming games?
We are not going to count web and streaming games toward your install count.
For now ;-)
People did not sign up for that kind of pricing model, when they opted to use Unity. Now they are commited, have invested ressources, time and have half finished products, they change pricing. So they might decide to change it again and charge for web games at a later point, for all we know.