This is absolutely false. The NSA asked IBM to not reveal that security against differential attacks was a design goal. They did not, as you suggest, allow the weakness to be present in DES (go read the Wikipedia article you cite again).
The NSA did make changes to the S-boxes used in DES at the last minute, and would not comment on the nature of the changes. Many people speculate this was the introduction of a backdoor. Last year at RSA a speaker from the NSA revealed that the (now 35 year old) changes served two purposes: 1. it actually fixed a weakness they had found, but did not want to disclose the details of. 2. scared the Russians into not trusting the now hardened algorithm and instead relying on older systems that they had attacks against.
The NSA did make changes to the S-boxes used in DES at the last minute, and would not comment on the nature of the changes. Many people speculate this was the introduction of a backdoor. Last year at RSA a speaker from the NSA revealed that the (now 35 year old) changes served two purposes: 1. it actually fixed a weakness they had found, but did not want to disclose the details of. 2. scared the Russians into not trusting the now hardened algorithm and instead relying on older systems that they had attacks against.