In the post, it is said, "CDDLv1 was not purposely incompatible with GPLv2".

That is a dubious claim. Because it's misleading, not because it's false. When you have an objective and you make a choice, you don't do so for negative reasons. But if you know the negative reasons exist and ignore them because the positive reasons are more persuasive, then what? Was your choice "not purposely made"? You knew things could go south, and then they did. It's irresponsible to say, "Ho, hum, who could have expected that? We didn't mean for it!" :-)