hello ,based on your information .. i am not sure what you understand by gratification phenomena and on what basis your child got diagnosed with this.
i am leaving respected dr diagnosis and based on your information ..your baby need detail development assessment ( specially all neonate ,infant reflex ,muscle tone
,milestone etc )
please be confirm that both legs n hand get tighten or one and which one ,side in which baby lying or upper side limb.
when baby tight leg n arm both get flexed or extended or mix.
in any other posture baby mimic something similar tightness in leg and hand .
any investigation like EEG happen ,any history of epilepsy