Will bitcoin-qt only recognize a bootstrap.dat file starting at block 1?

is it possible to use the python util to create a new bootstrap.dat starting at block 250001 ? For example - to update an off-line PC which has only had previous access to the 250k bootstrap.dat.

Creating a new 10gb+ file up to 270k+ seems silly when I only need to create the difference between the two (and easier to transfer to off-line PC).

Thanks.