There is no universal uniqueness requirement. The actual special or advanced knowledge standard and the supporting facts must be assessed.
Explain the relevant distinction
Identify the product, process or procedure, what the applicant knows about it and how that knowledge is used. Avoid relying only on seniority or a difficult-to-fill job. The company relationship, employment history and proposed assignment remain separate requirements.
What the statute forbids is an arrangement that amounts to labour for hire: one where the client principally controls and supervises the worker, or where the placement is not connected to a product or service requiring the petitioner's specialized knowledge. Knowledge of a proprietary control system, its configuration conventions and its failure modes is knowledge of the petitioner's product; general controls or millwright competence is a trade skill. Callum's file therefore has to be built on what the company itself created: the platform's critical-limit logic, the deviation and corrective-action workflows shaped by this group's product range, the lot-genealogy model, the validation record. L-1B also requires one continuous qualifying year abroad within the applicable preceding three, active entities linked through a qualifying parent, branch, subsidiary, or affiliate relationship, and U.S. duties that actually use the asserted knowledge.