I originally posted the above question to uMarketingSuite support as an email, here is the response:

That is great feedback and we did not considered this before. The inserted clientside script is only used for the clientside script: https://documentation.umarketingsuite.com/analytics/clientside-events-and-additional-javascript-files/additional-measurements-with-our-ums-analytics-scripts/.

It would be fairly easy for us to make sure that the GUID is rendered on a different element (non-javascript) such as and make sure that the script is using that guid. In that way you can whitelist the script or we can even make a separate js-file for this. So this is possible and I will add this to our backlog of items. We prioritize the backlog together with our partners (https://www.umarketingsuite.com/partners/) so I cannot promise you that this will be fixed in the next sprints.