However, you want to pronounce it is fine, but it doesn’t make it correct.
I don’t think there’s a time limit on announcing the way a creator prefers to pronounce the name of his creation.
It became an internet sensation, people asked him about the correct way to pronounce guf, he said how he prefers to pronounce it.
I prefer to pronounce it that way as well, as the original pronunciation by the creator. That’s more correct to me, but nobody’s forcing you to pronounce it any particular way.