Odd Lightroom behavior / Where does LR store photo edit info?

I'm experiencing something that should be impossible according to my understand of how LR works. It's my understanding that the whole point of LR is non-destructive photo edits. It was my impression that development settings were stored in a .lrcat file(s), NOT written onto the original photos.  If that's correct, then I'm at a loss to explain how this happened....

I copied some photos from my desktop to my laptop to edit while traveling. Desktop is running Windows 7, laptop macOS High Sierra, both running LR 6.0. I copied the photos only. I did not copy the .lrcat file from the PC to the laptop.

I don't believe I accidentally copied the .lrcat file because the order of the photos was different on the macBook than the PC. I believe re-ordering photos would be one of the functions of the .lrcat file. That would seem to explain why they appear in a different order on the macBook.

What I can't understand is why photos showed up on the macBook with star ratings and color coding. I thought no information was written to the photos themselves. I expected rating and color codings to be lost with the .lrcat file.

Furthermore, I'm 99% sure than development edits I made on the PC are also present on the macBook. I say 99% sure because the photos on the macBook clearly appear to have all the edits I made on the desktop like exposure, white balance, contrast, etc but nothing appears under the History section of the Develop tab. I guess the only way to be sure would be to make a change that is clearly undeniable like turn a color photo black & white, but it clearly seems the development settings came across without the .lrcat file.

This should be impossible right? I asked Adobe tech support. Their tech said the ratings, color codes and even develop settings are there because I copied over the .xmp files along with the original photo files. He stated that the development settings are applied to the photos on the macBook via the .xmp file. But the history of edits doesn't show up under the History window because I didn't copy the .lrcat file from the desktop to macBook.

I accepted that explanation on the phone. Then I noticed that ONLY the .CR2 files shot with my Canon have associated .xmp files. However, none of the .jpg's shot with my iPhone in the same folder have .xmp files. Yet the JPGs have the same ratings, color codes, and developing edits applied when open in LR on the macBook as the .CR2 files despite the absence of .xmp files.

So my question is, where are the edits I made in LR on my PC being stored? And how is it ratings and developing done on the PC show up on the macBook without the .lrcat file?