In my opinion, i believe that there is a slight difference between TDP and CDP. CDP is derived from the charts where you use either speed or time for the CDP.
TDP, eg if you are taking off from a long runway. You could be passed your CDP but because there is still sufficient runway remaining for you to land safely in the event of OEI. So, my TDP will be a point where i will deem not able to land the aircraft due to insufficient runway length corresponding to the speed and height at that particular point (where this is mainly DR) for me.
I stand to be corrected