I think it very unlikely they know anything about ABL.  
If I were in Don's shoes, I would be on the phone to all the relevant Principal Investigators. But as infectious disease specialists they may have decided the addition of ABL to a planned trial would be such a long shot that it would not be worth changing their plans, as it would require a bigger trial and therefore a later answer to whether chloroquine, or losartan, or one of the antivirals is effective.
Also, the addition of ABL to a planned trial would presumably also require the agreement of any companies already involved. That might have been a sticking point. So RVX decided they had no choice but to go it alone with the announcement. Just speculation on my part.