Have you read the rules for pre-approvals vs pre-quals for mortgages? A pre-approval for a mortgage must be a full credit approval subject only to finding an acceptable property.
From HMDA (on what is a pre-approval for HMDA purposes):
Application.—(1) In general. Application means an oral or written request for a home purchase loan, a home improvement loan, or a refinancing that is made in accordance with procedures used by a financial institution for the type of credit requested.
(2) Preapproval programs. A request for preapproval for a home purchase loan is an application under this section if the request is reviewed under a program in which the financial institution, after a comprehensive analysis of the creditworthiness of the applicant, issues a written commitment to the applicant valid for a designated period of time to extend a home purchase loan up to a specified amount. The written commitment may not be subject to conditions other than:
(i) Conditions that require the identification of a suitable property;
(ii) Conditions that require that no material change has occurred in the applicant's financial condition or creditworthiness prior to closing; and
(iii) Limited conditions that are not related to the financial condition or creditworthiness of the applicant that the lender ordinarily attaches to a traditional home mortgage application (such as certification of a clear termite inspection).