8.2 in 05 edition covers destructive testing as well. What they are refering to by Trepanning is a destructive test.
Trepanning is usually some form of boring. 8.2 "Destructive testing shall consist of the removal of completed welds, sectioning of the welds into specimens, and the examination of the specimens"
http://www.trepanningspec.com/index.html
By the prohibition of trepanning, they are clarifying their intent that the whole weld be cut out rather than a strap, or punch for testing.
It's been prohibited for a long time, but as I recall someone telling me many moons ago, people used to cut the strap, then weld up the hole rather than cut out the whole weld.

Regards,
Gerald

I think (and I am quite possibly wrong) that this method involves cutting out a coupon for inspection.  Trepanning also refers to boring a hole in a person's skull, an old medical practice.

Someone please correct me if I am wrong!

Trepanning is a lathe operation where a groove is bored in the face of a part, leaving a shaft in the center. The apearance would be like if You plunged a hole saw with no pilot drill into the end of a shaft, cutting a groove smaller than the outside diameter of the shaft, but not all the way to the center. This can be used to produce large diameter hollow bar stock.