All scoring is based on credit report info obtained from the CRA.
If a creditor does not report to a CRA, then it cannot be a factor in your scoring on any inquiry sent to that CRA.
However, the creditor may do their own internal scoring based only on their own database review of your account history with them, or the creditor might also pull your credit report from one or more CRAs.
Thus, your util of their line of credit, while not affecting your FICO score, might affect subsequent actions by the creditor, such as review for grant of any credit limit increase or for decrease of your credit limit or closing of the line of credit.
It is likely that their internal scoring algorithm may closely follow in effect those of the FICO scoring algorithm, so it would still be prudent to assume that high util might be viewed as a negative in your future evaluations, similar to FICO scoring criteria.