Why is wifi latency reduced when error model is disabled and laa signal received by wifi node is below -62 dBm?

[John Young]

I run laa-wifi-simple and wish to see the effect of laa eD. To reduce the involved factors, I disable laa dataErrorModel,  and make wifi plcp always successful received at the same time.  The distance is set so that the laa signals received by ap and sta are below -62 dBm. Then I  change the laa eD from -62 dBm to -72 dBm.  Laa latency increases as a result of waiting. I expect to see the wifi delay keep unchanged but indeed it reduces. It confuses me since wifi node is supposed to ignore laa transmissions. That means, ap's transmission is supposed  to be unchanged under both situations. Due to no error of packet reception, the delay is expected to be constant. 

Can anyone help me out?