very different to the likes of Opera Mini [...] In Cloudflare's case, the rendering happens on the server and only rasterization commands are sent to the clients.

Literally exactly what Opera Mini has done since circa 2005[0]. The main difference here is that Opera Mini progressed to the gp's "2025" scenario quite some time ago by adding limited support for events alongside OBML's rasterization commands.

[0] https://github.com/grawity/obml-parser/blob/master/obml.md