Not usual but if they picked up 100% of the gain on sale in the 1st year then it's no longer a installment sale of the property. It is a loan receivable with interest.  At that point you are correct, you can report it on Schedule B directly.

If less than 100% reported in the 1st year then you do use the 6252 every year whereby you report the principal and interest. The interest will flow to the Schedule B and the deferred installment sale gain will be picked up as 4797 or Sch D direct capital gains.