The rsync algorithm divides the file into fixed size blocks only on the sending side, then calculates checksums for all blocks. On the receiving side, it tries

The rsync algorithm divides the file into fixed size blocks only on the sending side, then calculates checksums for all blocks. On the receiving side, it tries to match them at all offsets, not just multiples of the block size. Thus, in your example, the first (and possibly the last) block won't be found, but all other blocks will be found, shifted by an offset of 1.