Statements are always benefited by research articles. For cervical rehabilitation Jull is tops. Please source and read the article below if you are interested in the evidence base behind deep neck flexor treatment.
Manual Therapy 12 (2007) 139–143
Original article Recruitment of the deep cervical flexor muscles during
a postural-correction exercise performed in sitting$ Deborah Fallaa,b,, Shaun O’Learya, Amy Fagana, Gwendolen Julla
Cheers,
SPPAWA