1) A mortgage is secured by a property and most bonds are not secured.
2) Mortgages can always be paid off early with no penalties and bonds can only be paid off according to much more restrictive call provisions. That means that mortgages are subject to prepayment whenever interest rates goes down. This is called "contraction risk"
3) A bond is issued by a company or government generally both of which have big cash flows. A mortgage is "issued" by a person.
4) A mortgage comes with an entirely different set of covenants than bonds do.
5) In the event of non-payment, getting paid on a mortgage involves foreclosure which is a very different process than bankruptcy.
6) The creditworthiness of a mortgage depends in large measure on the housing market and the creditworthiness of bonds depends on whatever the issuer of the bonds doees for revenues.
In short, an interest-only mortgage is almost nothing like a bond except that both are fixed income investments with similar cash-flows if neither is called or defaults.
So, no, not a very good question. Just a question by someone who hasn't thought much about the differences between bonds and mortgages.