Could password managers like 1Password (AgileBits Inc.) employ similar techniques? They seem to make very little effort in this regards. E.g. on 1Password, https://discussions.agilebits.com/discussion/101551/article-....
1. I created a new test-entry with a long and random password.
2. Opened the process's memory in the HxD hexeditor.
3. Ctrl+f
4. Found this password 4 times.
Even after i locked KeePass i still found the password 2 times.
This is bad!
Browsers implement Spectre/Meltdown mitigation on desktop OSes because without that, JS could read secrets from other JS contexts executing in the same process. One of the mitigations is in fact to just segregate JS contexts into different processes depending on the domain they belong to. But most apps don't execute untrusted code so most apps don't have this sort of in-process attacker to worry about.
Not really. Password managers have access information to your other accounts in the cloud. Your desktop may not have your most valuable data.