How are the interest-only, payment amounts typically calculated for multiple advance, construction loans?

The calculations completed in ComplianceOne mortgage follow Part I (A) and Part II (A) within Appendix D to Regulation Z which assumes that the amounts and timing of advances are unknown at or before consummation and that the interest is payable only on the amount advanced for the time it is outstanding.

Both of these sections indicate that the calculations are based on the assumption that one-half of the commitment amount (loan amount) is outstanding at the contract interest rate for the entire construction period.