If you don't want to be in a mortgage company long term I don't see an upside either for applications or for recruiting after school. You run the risk of burning bridges at the old or new company, and it is a tradeoff of showing loyalty and long term growth at a company vs a new role on your resume. Both can potentially be valuable in recruiting.
If you get into a good b-school recruiters will assume you have quant skills or you can showcase it with your GMAT. The companies that REALLY care for it (typically IB, HF or other high finance, some research roles, etc.) likely do so through some combination of a technical interview and test scores.
The only exception to me if I were in your shoes would be if you want to break into finance and the mortgage role is involved in the underwriting/credit side (not sales); that could be great experience. Of course, this is all assuming that compensation is similar for both roles.
Of course, it's your career, and if you feel the tug to make a move go for it!