Reassess the actual revised duties rather than relying on the earlier technical-publications description. The old title does not automatically cover the changed work.
Keep the current assignment in the record
Identify what changed, preserve relevant versions and explain the professional activity now proposed. Do not invent technical content simply to fit a category. A product-launch deadline does not guarantee admission or authorize work outside the arrangement assessed under the appropriate process.
A Canadian citizen can apply at a port of entry on the day of travel if the letter and credentials are complete, but the preparation — fixing the duty description, obtaining transcripts and resolving self-employment questions — typically takes several weeks. The usual failure is a slow start followed by a rushed choice: weeks spent waiting for an employer to confirm something informally, then a single week in which documents, a filing decision and travel all have to happen at once. Field seasons create their own pressure: an employer that needs someone in the woods for a specific window will resist a slipping start date, so agree the schedule inside the offer rather than around it.