Is the browser isolation product a "modern web proxy" that presents say, a social media management site (like Tweetdeck) or an internal app via a rewritten URL, rewriting the HTML, JS, and HTTP headers to hide authentication from the user?
If so - wow, to get that to work performantly requires deep understanding at all levels of the HTTP stack. I had a web proxy written in Haskell some years back that implemented online, nested HTML and JS rewriting and injection, and I was so close to getting modern web apps like Facebook and Gmail to render perfectly. Server side rendered sites were feature complete, but sites using a virtual DOM required care to proxy out DOM builtins like createElement and setting attributes, and that surface area is quite large.
For sites using chunked transfer encoding, it worked on a chunk-by-chunk basis, as opposed to blocking until the entire document had been transferred to the proxy. The additional latency was just the time to parse a chunk. Orders of magnitude better perf than any of the web proxies that many of us on HN used as kids to subvert school network restrictions, and much better compatibility.
It's a little sad my project never saw a release, but I would be very excited to see a company ship something very similar or even better.