Cherry: It is not a new minhag at all. You can see some very old cemetaries with the men and women buried in alternating rows, so that they are one in front of another instead of side by side.
One that I am aware of is the southern street cemetery in Baltimore, which is well over 100 years old.
As far as the avos, I don’t know what information you have that they are buried side by side instead of one in front of the other.