I asked Cento the same question, and here is what they told me:
Cento Certified San Marzano Tomatoes have been, and continue to be grown and produced in the Sarnese Nocerino area of Italy. They continue to follow the same high quality standards that Cento has always stood by.
After our new crop was approved and certified authentic, a new organization was appointed to govern our labels. After months of delay in their response, we were notified that our label design no longer conformed to their requirements. Due to the unreasonable nature of the new label requirements, Cento has decided to remove the DOP seals from its label; however, they remain Certified San Marzano Tomatoes and continue to follow the same high quality standards.
Our Cento Certified San Marzano Tomatoes are certified by the largest third party certifying body in the European Union. We assure you, in no way has this product's certifications and quality standards changed. Your are paying for the same certified, high quality product, sure to beat any other certified San Marzano tomato brand. Thank you for submitting your inquiry regarding Cento San Marzano Tomatoes.
Cento Fine Foods, Inc.
FWIW, I prefer the Cento Italian (in the 35oz can). They are half the cost, more tomato, and IMO, taste better than most any other tomato. It's just about all I use.