Erm, quoted from the exact announcement you linked (including the typo):

> These consulting services do not constitute anaudit or attestation engagement

They're saying themselves that they weren't audited.

Not quite--they're saying that the consulting services that Friedman offered on top of the audit procedure they were hired to do are not an audit. Friedman audited Tether, but it was not "a full audit" (https://www.coindesk.com/tether-confirms-relationship-audito...) and, according to Tether, the reason for the that is as follows:

>Given the excruciatingly detailed procedures Friedman was undertaking for the relatively simple balance sheet of Tether, it became clear that an audit would be unattainable in a reasonable time frame. As Tether is the first company in the space to undergo this process and pursue this level of transparency, there is no precedent set to guide the process nor any benchmark against which to measure its success."