IMHO it is highly likely that RaTG13 was fully sequenced in 2018 in order to implement one of the early actions in the DEFUSE program (analysis of samples/sera of interest).
Possibly they cultured it at the time indeed.
See "Subtask 6.4 Test previously-collected human sera from Yunnan Province to assess SARSr-CoV QS spillover (WIV)."
Also RaTG13 would have been a good candidate for a low abundant high risk SASRs-CoV - after all it likely killed 3 people, or at least contributed to their death. 
It is quite possible that all there is behind the obfuscation around RaTG13 is 'just' the strong reluctance to show that China was running ahead with the DEFUSE proposal.
Officially they were not supposed to be doing this (no part of any approved project with Western partners)
Most importantly that would also show that China was potentially capitalizing for its own purposes on know-how and technology from the cooperation wrongly pursued by Franz /Callahan via EcoHealth Alliance.
Track II gone badly wrong.
The CTR worked in the USSR because the USSR was delinquent at that time, AND because the USSR was anyway ahead of the US on the related technologies.
Something that some seem to have missed.
Here the US is the one ahead. And thus China could be tempted to use that US DURC technology and know-how for its own purpose.
At least Callahan, even if he may be a bit short-sighted on the potential of Track II succeeding in China, is not so naive on the safety shortcuts that China is ready to take to get ahead.
Quite a different tune from Franz, who is also an adviser to EHA.
@threadreaderapp compile