Subject and Verb Agreement - When to use Singular / Plural

I see below suggestion in Grammarly on Subject and Verb Agreement.

"The verb needs does not seem to agree with the subject that. Consider changing the verb form."

And they give below examples on this as suggestions:

***Incorrect**:
Tom and Jenny loves entering trivia contests.
**Correct**:
Tom and Jenny love entering trivia contests.*

***Incorrect**:
The book, including all the chapters in the first section, are boring.

**Correct**:
The book, including all the chapters in the first section, is boring.*

As an explanation, they say "A singular subject requires a singular verb, and a plural subject requires a plural verb. "

But in the above example that is not the case, Tom and Jenny are two people and they use love and not loves. Can anybody clarify me on this? Thanks