That’s a really nice and detailled article,I like it 
I just want to comment on one statement that is wrong: “C# and .Net doesn’t exist on Haiku yet” - It was ported as a GSoC project in 2023 and while it’s not completely upstreamed yet and still somewhat tricky to use,it does exist.
More info: [GSOC 2023] .NET Port
Also,the situation with JS-heavy sites in WebPositive may drastically improve with the switch to WebKit 2 which allows to split stuff in multiple processes,a slow page will no longer slow down your whole browser.