[samatman]

30% of 2016's cobalt consumption is 34800 tonnes. Most cobalt is used in alloys[0], and it is mathematically impossible that each of five companies uses more than a third of the supply in any case.

In other words, it's quite possible that any, or even all, of those companies don't use DRC cobalt. I'll grant you that it's unlikely, particularly in Tesla's case, given how many batteries they produce.

[0] https://en.wikipedia.org/wiki/Cobalt#Applications