Have you noticed how often people complain Chrome uses too much memory?
If you pre-initialize the renderer and JavaScript engine and then fork that pre-warmed instance for each site, every page of memory not written to remains shared in physical memory.
Properly accounting for that in task managers is hard, though; on many OSes, Chrome's memory usage looks much scarier than it is in reality.
It'd also weaken any security protection based on randomness (eg ASLR slide, pointer encryption keys).
https://source.chromium.org/chromium/chromium/src/+/main:con...
If Chrome itself is not aggressive enough, try the "Auto Tab Discard" extension.
Safari on the other hand doesn't even have Tab Sleep for whatever reason.