It's surprising that public records showed property larger than it really was; generally, it's the other way around (built without permits). I've only come across this issue a few times, so your experience is remarkable. Local building inspector not physically visiting property or plans not reviewed, or builder fraudulently misrepresenting what he was selling?? Odd.
2 instances I ran into where the actual GLA was smaller by about 12%, the builder/developer had the larger square footage in the brochure, with statement that the actual finished space may be different. The sketch on the high-rise condo revealed the size was short, and buyer renegotiated the $$$sale price.
In measuring the other new construction house in Beaumont, it felt smaller than expected, and appraisal showed GLA was short about 15%. Buyer sued seller/builder (& won $$$), insisting they were not getting the square footage they were paying for.
The 3rd case was a very old building in the Crenshaw District, where a portion of the original structure, probably a sunroom or dining area, was missing. It was clear where that indoor space had been part of the original house. That one was unforgettable, because there were very noisy wild parrots flying all over the place. Apparently some birds had escaped captivity long ago, and made that area their hangout. Soooo loud!