The rectus capitis muscles are often implicated as causing suboccipital headaches, 
but, as you can see, the trigger point referral pattern is over the ear or in a "sunglass" pattern, as we often teach in our dry needling seminars.
That is not to say that dysfunction of the muscle can cause suboccipital headaches through dermotomal and sclerotomal referral patterns (1).
We know that there are attachments of the suboccipitals to the dura as well (2), and these muscles are shown to upregulate tone with "head forward" posture (3). It would stand to reason that we would want to treat them. Here is a video with a "clinicians eye" view of those muscles and how to treat them.
1.Luedtke K, May A. Stratifying migraine patients based on dynamic pain provocation over the
upper cervical spine. The Journal of Headache and Pain. 2017;18(1):97.
doi:10.1186/s10194-017-0808-0. link to free full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615079/
2. Luis Palomeque-del-Cerro; Luis A. Arráez-Aybar; Cleofás Rodríguez-Blanco; Rafael Guzmán
García; Mar Menendez-Aparicio; Ángel Oliva-Pascual-Vaca A Systematic Review of the Soft-Tissue
Connections Between Neck Muscles and Dura Mater: The Myodural Bridge SPINE. 42(1):49–54,
JAN 2017
3. Richard C. Hallgren, Steven J. Pierce, Dhruv B. Sharma, Jacob J. Rowan. Forward Head Posture and Activation of Rectus Capitis Posterior Muscles. J Am Osteopath Assoc 2017;117(1):24–31. doi: 10.7556/jaoa.2017.004.
