"Taking someone else's spot"

[Drolefille]

Originally Posted by Titchou

I give..whatever...let them just release whomever they want for whatever reason they want. No need to question anything.

It's perfectly 'legal' to release them. This isn't a "no need to question anything" situation. The process is overseen throughout. Because it says "may" it means that a campus "may" enact those rules. A later section of the green book provides sample rules for recruitment including:
For Chapters

FSR, PSR, MSR: A woman shall attend orientation and membership recruitment events to which she has accepted invitations. In case of illness or an emergency, the woman shall notify the Panhellenic and/or her recruitment counselor. The Panhellenic and/or the recruitment counselor will then notify the chapters involved.

For PNMs

FSR, PSR: A woman shall attend orientation and all parties to which she has accepted
invitations. In the event of illness or emergency, she should notify Panhellenic and/or her
recruitment counselor if she cannot attend.

Although this doesn't list the consequences, the previous bit did. I'm confused why you're assuming it's wrong and should be reported just in case, when it's really not uncommon on campuses in general AFAIK, and is permitted- although not necessarily required - by the manual.