Hey just to rub it in here is the official Microsoft statement on the bug.
Edgar explains that it needed to detect the browser being used because not every browser supports prefetching. While a technique it used worked with Safari on Mac, it hung for Chrome on Linux.
"The second technique does not hang on Safari on Mac, but it does on Chrome on Linux. We will definitely ensure that more Linux testing is done."
What do you know, it was a compatibility issue where different solutions were used on different browsers and changing your User String would result in a different code path working better.