start of week is different for running v activity minutes

Yeah unfortunately this is a long standing complaint that Garmin has never addressed except to say "that's how it works".

https://support.garmin.com/en-CA/?faq=pNU9nnDzzGAHmEavp9rpY8 

Can I Change the Day of the Week My Intensity Minutes Begin?

You cannot change the day of the week your intensity minutes begin. They are accumulated weekly from Monday–Sunday. Changing the First Day of the Week setting in your Garmin Connect account settings only applies to your calendar and related features.

Don't expect from a watch company to understand nuances of time... Garmin is not alone in this. I see it with many American companies that either they don't know that there's a whole globe or they don't understand things like timezones, l11n and i18n, etc