A coder's [or a spy's] definition of what constitutes acceptable intrusion under the Fourth Amendment, or what constitutes "metadata" as opposed to "data" is arbitrary, situational, and unacceptable. The definition needs to be made by the legislature, signed by the executive and subjected to scrutiny by the judiciary.
Not by appointees.
Not by bureaucrats.
Some of the other things I cited are not normally considered "metadata." Nevertheless, they are being illegally gathered. Because everything is being gathered. And if you think it isn't, or that any of it isn't being looked at, you're naïve and mistaken.
What is most shocking is that there is no need to collect it. Paul missed a golden opportunity the other night by getting into a childish shouting match with an oaf instead of pointing how exactly how good the targeting technology is, and how it doesn't have to be aimed at US citizens.
Being in tech for a couple decades I have had a chance to dip into a small portion of everything. I can guarantee that everything is not being gathered. But a lot of personal stuff is.
But your main point is very valid: the distinction between metadata ("ok" to gather) and what I defined as data is arbitrary and dangerous to liberty. There is no way we can allow metadata to be acceptable just because some says it is metadata and someone else says metadata is ok.