Emergency Exit Access
An aircraft interior design layout has to be approved by the relevant airworthiness authority; for new European aircraft today that’s EASA. The requirements for accessing emergency exits for new designs are contained in CS25.813.
The A320 family of aircraft was certified to JAR 25 at change 11 (I think) – pre EASA. As a general guide for over-wing exits, the opening must not be restricted by anything, including loose table, reclined seats etc. hence the requirements you note.
UK CAA document CAP 747 has nice drawings and simple language under Generic Requirement No.3 for access to Type III and Type IV exits.