BOVS diagrams must be complete, while also serving the point you want to make.
Diagrams must be complete: no Party may be omitted. This ensures diagrams never mislead by suggesting that structures are simpler than they truly are.
Which Parties must be included for a diagram to be ‘complete’ is determined by your diagram’s Focus and Depth.
However, you may consider only some Parties or interest Chains to be relevant to your point. If so, there are ways to collapse or diminish the other parts of your diagram while maintaining an accurate portrayal of the situation:
If you use an Optional Feature that applies only to relevant parts, then you must also draw non-relevant parts less prominently. This ensures readers understand why those Optional Features are not shown elsewhere.
Unless you explicitly decide otherwise, all parts of your diagram are assumed to be relevant.