The gravel stabilizes the tar somewhat. But yes. And gravel washes off the roof too. And then the roof leaks the next time you get rain. They’re typically initially installed with hot asphalt and then patched with tar until the homeowner gives up and buys shingles. There’s a good reason you don’t see gravel roofs very much.

We’re plural. Our lived experience runs contrary to your opinion.

We aren’t born with our personalities already intact, they develop and unify around the age of 5-6, and DID is a response to trauma from before that age.

That’s the current prominent theory, but testing it empirically would be disastrously unethical.

Here’s the relevant section of the DSM:

https://archive.org/details/diagnostic-and-statistical-manual-of-mental-disorders-dsm-5-pdfdrive.com/page/291/mode/2up

All dissociative disorders (quite possibly all disorders, we haven’t read the whole DSM) require the presence of clinically significant distress or impairment in order to be considered a disorder.

There is no specific entry for nondisordered plurality for the same reason that there is no entry for individuals who do not experience mental disorder: The DSM catalogues mental disorders, not the entirety of the human experience. It’s beyond the scope of the document.

Here’s a good introductory primer to plurality:

https://morethanone.info/

They use tar.