FEMA P-2082-1 2020 Edition - Figure C12.3-6

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Source: NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (FEMA P-2082-1) 2020 Edition - Figure C12.3-6

Hi, I've been learning on how to check on redundancy properly and came across this helpful flowchart from NEHRP. I have 2 questions though.
1. As far as I know, ASCE 7-16 (TaBLE 12.3-3) doesn't state anything regarding increasing demand above 50% when removing beam moment restraint. Why NEHRP state so?
2. Again ASCE 7-16 (Table 12.3-3) doesn't state anything about plastic mechanism analysis to check if there is more than 33% reduction in story strength. Why NEHRP state so? Why does it have to use a plastic mechanism analysis?