i have heard of coffin slicing before, not from matilda. i think this practice may be more common in rural areas, with small cemeteries where there are no watchmen. i know some people would hire someone to look after the grave for a few days.
an idea of re-using the coffin is very "green". both figuratively and, after few days, literally as well.
And that is where my grandmother and uncle(her son) are buried, in a rural cemetery in el Cibao. She wanted to be buried where she was born and raised. Thus the reason why the glass of the coffins were broken prior to burial.