OK this got sort of answered in Slack. Short answer, it doesn’t appear to matter too much unless you need to have a theme that totally follows the standards and plays well with all the other kids.
In “Pinegrow WordPress Starter Theme 2 Basics” under first export the ST2, there is a part where it says:
" IMPORTANT Don’t change the theme name and theme slug yet. This part will be evocated later."
I haven’t found anywhere that this is mentioned again. When does this get changed? I don’t want to go too far if it means I have to unravel everything to get these to the correct values.