IS UPDATE 13.7 JUST FOR COVID19 TRACKING?

No.

highly unlikely that's the only thing updated in the release..

but the other stuff is not specific, just says 'other bug fixes'

https://support.apple.com/en-us/HT210393#137

It's also not 'covid19 tracking', it's exposure notifications, which you have to opt into. Even if you opt in, its still not capable of 'tracking' you.

https://covid19-static.cdn-apple.com/applications/covid19/current/static/contact-tracing/pdf/ExposureNotification-FAQv1.2.pdf