Agreed, it makes sense for a few reasons, so I realised at the time.
a) You don't need to reset if you have a site with intermittent issues (as at G3 tamper should be eng reset)
b) It displays on the keypad and log as a separate event to a tamper, increasing your information for diagnosis.
c) Mask on most controls is above 10K, having this huge shunt resistance increases the threshold of any fluctuations from the reed.