poor analogy, but let's explore it anyway... let's say my intent is to send 1000 bitcoin to an heir (i fucking wish). as part of that transaction, I want to embed arbitrary data which states my final will and testament, and confirms that the recipient of that bitcoin is the rightful owner as validated by my embedded will. is that a monetary transaction?

Yes. The arbitrary data is not part of the transaction. The fact that the recipient can unlock the address means they are the owner not some arbitrary statement to be interpreted later. The transaction can be made without the data so why include it? The private key + spending condition is the only thing that matters.