Checkpoints would require a TW attack to start after the CP, and is a manual intervention.  The devs probably did it to help restore calm more than anything else.

However, there may be a way to obsolete the need for adding this type of checkpoint to prevent TW and similar types of attack vectors in new coins.  The threatened attack has caused me to offer a minor new thought on the matter, but it is more the sort of thing that ought be implemented with care, not as a haphazard incident response to a threatened emergency.  

This notion may also be entirely wrong headed and need to be reworked a few times before it makes it into codebase, if it works at all.  The take home message for me is that we don't always have the luxury of advance warning for an attack.  This idea, or something like it, is needed for an ongoing protection in perpetuity.  I've left it with the dev team to evaluate and am comfortable that they are capable to do so.