Franz's translations always struck me as the kind that would come from someone who was old-school trained in Classical Greek. His rigid adherence to translating Greek constructions into English being my main example.
The NWT* loved the continuous tenses and rendered them slavishly in English. For example, where most modern translations would say "Seek the Kingdom of God", the NWT** would have "Keep seeking the Kingdom of God".
Quite often a translator of a contemporary translation might translate the imperfect tense into a simple past tense rendering. The NWT would try to keep the tenses the same (and try to reflect the Greek "aspect"). So where a modern translation might simply say "went", the NWT would say "was going".
So I have no doubt that Fred had some formal training in Classical Greek. But his translation is way more rigid than it needed to be, especially considering that Koine Greek is somewhat less formal in form.
*I'm remembering things about the NWT that existed twenty or so years ago, not the current revision. I haven't had a good look at it.
** Doing this from memory. Judge the spirit not the letter, please! 😉