new options improving fencing were added in 3.5, however default was left as is.
Generally people do not follow all the new config possibilities and leave the system as previously configured. It makes sense most of the time, however with fencing both features tremendously improves product experience - they finally make fencing useful, so why don't we enable it by default?
I'm not aware of any adverse effects, hence I suggest to enable them by default so all the users can enjoy them out of the box