HubScore is computed as follows:
- Amount of traffic - including percentage from reputable sources other than HubPages
- The reputation of the Hubber - your Hubber Score and contribution to the community
- The response of readers to your Hub - including comments, thumbs up, etc.
- The uniqueness of content - copying content already available on the web will be penalized
You can see that linking to non-relevant Hubs isn't mentioned there.
There are other reasons for NOT linking to non-relevant Hubs.
One, most of your readers find your article because they're looking for information on a specific subject. You're going to annoy them by providing links to irrelevant material.
Two, if you write a short Hub then include links (e.g. in a RSS feed) to many irrelevant Hubs, you may dilute your keywords.