Sure but I was responding to the point that a diary can't be searched. It can be. The key difference is that doing this for analog conversations was expensive for the police as it required them to devote finite human time. Digital is not the case.

Comparing to analog is I think flawed because even if it mapped 1-to-1 it does allow for a level of search that is problematic given the low cost of digital surveillance.

Testimony under oath can be compelled

In theory. In reality, no. "I don't remember/I don't recall" is a famous dodge.

Yes but people can genuinely forget the exact words they spoke time ago, even one minute ago, or a whole conversation. Examples: Who did I talk to yesterday? Did I met that neighbor of mine yesterday or was it the day before? I don't know.

I think generalizing forgetting information ignores that certain conversations would likely have a better chance to be remembered

They are not the same thing.