Consolidation or Joinder in B101: Allowed or Prohibited?

As per Black Specs Question, seems Joinder is prohibited by B101. Researching more in deep, I had founded several authoritative and conflicting opinions, which is the truth?

Prohibited: 

"Professional Practice, A Guide to turn Designs into Buildings" Paul Segal FAIA, page 88

again page 115

Allowed:

Michael Hanahan, B101 Conference

https://youtu.be/gDNRGtq0Hp8?si=Ir9R3U7QW4UMvZ6O  Minute 1:35:20

As far I understand from the same B101