A JW friend of mine (who was one of my besties until I told him I didn't believe JW religion anymore) used to live in Austria and for a while in the 70's was in the same congregation as Losch. They used to spend some time together in the ministry. My JW friend tells me that he and Losch used to often talk about how they believed the WT was wrong about certain interpretations of the bible, for example, how at the time the WT taught that the mustard tree used by Jesus in an illustration represented an evil kingdom, and Losch and Friend didn't think that was right.
Then Friend tells me that when Losch was appointed to the GB, many of the things they disagreed with and put forth alternative explanations to became new light. Losch changed some old understandings or influenced their change when he joined the GB.
The conclusion then is, that if Losch secretly didn't believe certain doctrines or interpretations and discussed them with Friend, then he was an apostate by the JW definition of the term. Isn't it considered apostasy if you believe something different and then share your thoughtcrime with others? Losch was an apostate by JW standards then.