From page 28 of the GIR:
Dwelling. Dwelling means any residential structure, whether or not attached to real property. It includes vacation or second homes and rental properties; multifamily as well as one-to-four-family structures; individual condominium and cooperative units; and manufactured and mobile homes. It excludes recreational vehicles such as boats and campers, and transitory residences such as hotels, hospitals, and college dormitories.
There would be no mortgage recorded against a MH only loan either. The regulation says if the loan is secured by a dwelling. Your loan is secured by a dwelling, therefore if it's for a home purchase, home improvement or refinancing it's reportable.
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The opinions expressed are mine and they are not to be taken as legal advice.