USAV Modified Rules

[Paul Vancouver]

USA Volleyball (USAV) rules are prefaced with this text:

MODIFICATIONS
For all designated international competitions, the FIVB rules will be fully in effect. USA Volleyball recognizes that there are circumstances where grassroots development, sport development, safety or insurance requirements would indicate a need for a temporary rule modification (i.e., the number of substitutions might be expanded to include more participants at a school or recreational level.)

Acknowledging that a rule may not be changed, in instances where the USAV member organizations feel that the promotion of the sport would be enhanced by temporary adjustments, they are encouraged to promote the advancement of the sport.

In an attempt to have continuity in the domestic play of the game, this document has inserted in designated “USAV” boxed areas suggested guidelines for some of the more common temporary adjustments used to promote the growth of the game.

EXAMPLE:
USAV 1.1: The free zone may be a minimum of 2 m (6’6”). It is not required that the free zone be symmetrical.

What do phrases like "Acknowledging that a rule may not be changed", "temporary rule modification", "suggested guidelines", and "some of the more common temporary adjustments" really mean?

Is there anything temporary about the differences between USAV Domestic Competition Regulations and FIVB Official Volleyball Rules?