the statment contains two different points .
1. About the building,construction.
This basically means in (the most unusual) case of planning people coming along and saying that your unit is built against P.P. and must be dismantled you cannot sue the owner/landlord. Having rented in dozen retail premsies over thirty years in and out of shopping centres I know that there have been thousands of cases of sub-divisions of larger units that have not obtained P.P. I've never heard of a problem with any of them.
But ,just in the miniscule chance of a problem ,you are -in effect- getting fair notice that you can't sue the landlord if there is a PP problem.
A lawyer will -correctly in law-advise you to check that all is OK re planning for the sub-division. Such advice may mean a long wait for a positive response from the planners.
2. It's obviously up to you to ensure there's no PP problem regarding your own use of the premises. But you need not bother to get PP if its a normal retail business (the serving and eating of food is another matter).