Is XXI restricted from engaging in those kinds of arrangements or do they have to have "arm's length" relations when it comes to coin acquisitions?
I don't think so.
This first buy is still meant to be a "capital building" event through a PIPE agreement.
While I am typing this, I think it would not be a positive development if Tether acted as a "market arm" of XXI Capital, selling them its bitcoin.
However, I hope this is not the case.