I don't understand. They are redirecting to their own S3 bucket, so who would be the recipient of the leak?
Also, isn't this what Referrer-Policy is for? https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/...
Blogger predates the existence of this header by many years. Blogger, I believe, has also been in maintenance mode for many years.
Quoting web standards, you are more optimistic than I am, unfortunately, nobody uses them consistently or accurately (look at PUT vs POST for create / update as a really good example of this - nobody agrees) its a shame too, there's a lot of richness to the web spec. Most people don't even use "HEAD" to ensure they aren't making wasteful REST calls if they already have the data.