An employer’s confidence in the explanation does not itself grant TN status or authorize U.S. work.
Resolve the case before relying on the start date
Obtain the appropriate immigration decision and status for the real assignment. Keep document requests and the employer’s preferred start separate; a pending request to the school is neither an approval nor an automatic extension of existing permission.
Use that deadline to obtain the acquirer's written confirmation of your employer and duties, so any necessary new letter or petition is ready in time rather than assembled during a delay at a port of entry. An in-person application at a land border or preclearance facility produces a same-day answer with no visa required; an employer petition on Form I-129 takes longer but leaves a written record and a decision that can be reviewed before anyone travels or resigns.
Set a specific milestone for receiving corrected, consistent documents, and only build the rest of the timeline, including any planned start date, around the confirmed corrected assignment dates. Start by confirming which documents exist and in what language, since ordering an evaluation before the underlying transcript arrives simply moves the wait rather than shortening it.