Interesting. That's very subtle behavior. (Especially since it sometimes fools one into thinking /g option is not enabled when in reality, it's a CR+LF issue.)

I'm not saying your site's interpretation of Windows CR+LF is "wrong" but the other 5 online[1] regex testers don't behave that way on Windows Chrome browser. I also tested the regex and target text on desktop JGSoft RegexBuddy[2]. None of those required "\s\s" instead of "\s".

Debuggex at the least, is very idiosyncratic since the majority of the other testers don't treat CR+LF that way.

[1]regex testers tried with "([A-Z])\w+\s\w(\d.\d)" on Windows:

http://regexr.com/3b22q

http://regviz.org/

http://www.rexv.org/

https://regex101.com/r/eB5jY1/1

https://www.debuggex.com/r/mci3WLNmHGTEatf6

[2]http://i.imgur.com/t2L04mO.png

(http://www.regexbuddy.com/)