Potentially, if the complete role fits the listed profession and the applicant meets its requirements. Examine whether training supports professional engineering work or whether the job is principally sales, general instruction or another activity. A percentage inserted into a letter does not override the work that will actually be performed.
Use a real project to explain the role
Take one planned equipment installation. Identify what the applicant designs, what technical judgments they make and what they teach the customer afterward. The employer should explain who handles sales and routine support if those functions belong elsewhere. Keep the description consistent with internal job records and the contract; do not present a redesigned role that the employer does not intend to provide.
For TN purposes the question is whether the whole of the work is professional geological practice, described clearly enough that an officer reading the letter sees one qualifying assignment rather than a mix of professional and technician tasks. The applicant carries the citizenship requirement, since the principal must be a Canadian or Mexican citizen, along with the qualification requirement attached to the specific listed profession, which a degree earned in an adjacent field does not automatically satisfy. No expenditure cures a category mismatch: TN still requires Canadian or Mexican citizenship, a USMCA-listed profession, its particular qualification, and prearranged US work that is not self-employment.