Is this the same as a defrost sensor like DA32-10104N or DA32-00006W?
No - this is a bi-metal defrost thermostat. DA32-10104N and DA32-00006W are defrost sensors, a separate part, so check which one your repair actually needs.
Should I replace the defrost heater at the same time?
Yes - it's advisable. The defrost heater and this thermostat work together to run the defrost cycle, so if one has failed the other may be worn too.
What symptoms point to a bad defrost thermostat?
Frost or ice that keeps building on the evaporator because it won't defrost, sometimes with a defrost error code. A failed defrost heater or sensor can cause the same symptoms.
Will this fix water leaking under my crisper drawer?
Usually not - water under the crisper is most often a clogged or frozen drain line. Check and clear the drain, including the tubes to the pan by the compressor, first.
Can this replace a DA47-00133B thermostat?
No - it isn't listed as a direct replacement for DA47-00133B, so it can't be guaranteed to work correctly or safely in models that used that part.