Those categories are from ISO 21930, Section 7.2.12 (table attached).
The clearest guidance on the issue I’ve read is the ACLCA’s 2019 guidance on calculating non-LCIA inventory metrics. Biogenic stuff starts on page 32:
From what I understand, the emissions aren’t so easily assigned to a single phase in a cradle-to-grave LCA since biogenic carbon also leaves/enters the life cycle during other phases too, like A5 (waste during construction) or B phases (replacement of worn materials).
Hope this is a start!