I suspect the strata manager is correct. Payments having to be made by the owners corporation are funded according to the unit entitlement of each owner. I am confused about what you are trying to do? Take our a loan to cover for owners who do not pay the special levy? That’s not going to work, if that is the case.
In your shoes, I’d either take out a loan for all the work, and negotiate that it can be paid back early, as levy amounts come in. Or skip the loan, and raise it all by a special levy, and leave it up to individual owners to get loans for their part of the money. Keep in mind that the special levy is like other levied amounts, and owners who fail to pay are charged interest at 10% annually, which would occur regardless of loans etc…