I've often thought it would be better to allocate sunbeds to rooms (in fact I'm sure there was a hotel that did this ). However, the same scenario would happen as in the article's photo, folks would be getting up at the crack of dawn to 'mark their spot".
When we stayed in an apartment overlooking the beach in Carihuela, I'd watch the sunbed lady setting up on the mornings. I noticed she'd put towels on certain beds each day, folks had paid in advance to have "their spot" on the beach for their holiday duration. Tough titty if you wanted to be front row near the sea, they'd already been booked before you arrived