Re: Suwari Waza
That great long article about stretching with its citations rather parallels the advice that's going around the ranks of international competitive sport where it's a really bad thing to injure an athlete.
Injure an aikido person and - boo-hoo - a few training sessions are missed and someone limps around work with "ooh I pulled my groin but.. grab my wrist".
Injure a professional or Olympic athlete and either an income or a decade's training is lost. I'll go with the academic claptrap..