In Bodhidharma's case "wall gazing" likely meant not a physical posture but maintaining the mind like a wall, that is, without discrimination or attachment to emotions and ideas.
"There is no such thing as the real mind. Ridding yourself of delusion: that's the real mind."
(Sheng-yen: Getting the Buddha Mind, p 73)
“Don’t rashly seek the true Buddha;
True Buddha can’t be found.
Does marvelous nature and spirit
Need tempering or refinement?
Mind is this mind carefree;
This face, the face at birth."
(Nanyue Mingzan: Enjoying the Way, tr. Jeff Shore; T51n2076, p461b24-26)