You are not the first person to raise this issue with respect to the interpretation of Schedule IV in RIC-13. Essentially, your question, refined to its essence, puts the issue most succinctly:
If a certain channel does not have a specified usage in the area in question, may a recreational boater use it?
The answer to this question is, yes. In the absence of any specific prohibitions or a specific international/domestic or regional service designation, that channel can be used for any intership purpose that the user wishes.
Obviously, safety channels and calling channels must be used for their intended purpose in order to optimize the chances of a safety call being heard. Other channels, in various geographical regions of the country, are reserved for specific purposes or services, and as such are indicated in RIC-16.
As this document is currently under revision, we will take this opportunity to insert a statement of clarification to this effect.
Thank you for bringing this to our attention.
Technical Policy Analyst
Radiocommunications and Broadcasting Regulatory Branch