If you only paid property taxes on your primary home via a 1098 Form, then list it in that section along with your mortgage interest. There are a number of reasons for the two separate property tax sections, such as;

1.) Not everyone has a mortgage so there would be no 1098 form to report the property taxes on.

2.) For mortgage holders, not every lender will list the property taxes on the Form 1098 (IRS does not require it)

2.) For homes sold/purchased, property taxes listed on a closing statement will not be reported on a 1098 Form at all.

4.) Property taxes for land held for investment and no mortgage held is entered in the property tax category.