Solvent shell collapse

In "advanced organic chemistry part A" book page:306&307 , the author uses the term ‘solvent shell collapse’ when talking about the reason for retention of conformation in tertiary benzyl systems (under hydrolysis reactions) where he states that some of the reason for this retention might be the collapse of solvent shell in the front side of ion pair, the difficulty in solvation from rear side due to bulky tertiary system and hydrogen bonding between anion and water molecule which facilitates the capture of water molecule from the front side of the ion pair.

Could you clarify more about the reasons? what is solvent shell collapse? and why does the bulky tertiary system affect the direction of nucleophilic attack on the planar carbocation as the nucleophile attacks from above or below the electrophile?