Why, though?
It’s a newspaper article giving suggestions. She’s saying a versatile t shirt dress would be a useful thing to pack. You don’t have to choose that one - you could probably find one at Sainsbury’s.
Most of the items are inexpensive - and a good wardrobe needs a balance of high and low to have some individuality and swagger. (Aka style.)
(For myself, I dislike buying things just for one event, like a brief holiday, so I’d want a t shirt dress good enough to wear in everyday life once returned. Far better one decent one than half a dozen £14.99 versions that would lurk around my wardrobe never being worn further than the garden for the rest of the summer. Though I should say I’ve never bought anything from Sezanne as it’s not my style.)