It is weird. And really this report comes down to them getting a couple of signed letters from third parties. Why do it this way rather than a normal audit?
A positive interpretation is that Tether is solvent and wants to prove solvency but does not want to deal with non-solvency related audit issues. That's assuming some goodwill... If you don't assume goodwill, what you should conclude from this is anyone's guess.
Designed to distract and deflect. Goodwill on financial solvency matters was completely destroyed after they suspiciously "dissolved" their relationship with audit firm:
This is somewhat reminiscent of Michael Cohen's "proof" that "[he has] never been to Prague in [his] life." (in his case, a picture of a cover of a US passport). It is not actually proof of anything useful, but does manage to help control the narrative in a specific way