Terry, I appreciate your highlighting this particular navigational error of the WTBTS.
My Mom said that she had a "Bible Student" in 1962 and had explained to the student this scripture with the then current understanding that the Higher Powers were Jehovah and Jesus, as you pointed out that JW's believed from 1929-1962. The person with whom my mother was studying confidently disagreed with her explanation, however, Mom stood by what the Faithful and Discreet slave had taught and defended the position.
Mom attended the District Convention in the summer of 1962 when this "new light" was explained in a talk. Mom tells that after the convention, she had to go back to the "student" and explain that she (the student) had been correct and my Mom humbly took the blame for not understanding it correctly. I don't think this "student" ever progressed to baptism, but I recall my Mom saying how embarrassing it was for her.
It is scriptures like this, Romans 13:1-7, that with basic reasoning skills the interpretation is quite clear. The fact is noteworthy that Christendom always knew who the superior authorities where when WTBTS did not.
For me personally, this was one of those flip flops that I learned when but a child that threw a red flag up that raised concerns about Jehovah's Witnesses teachings. Unfortunately, it took me another 40 years to wake up:(