Burial Registers are just that - a record of a burial in the Church or Church Yard. A note would be included if the burial took place in another parish.

It was not required that a burial took place in consecrated ground which is why many deaths do not show up in the Parish Burial Registers.

Stones/Memorials, if any, would be errected some time after the death, some times after a considerable period.
The inscriptions have to be read carefully. A name on a stone does not necessarily mean that the body was buried there.