Inspired by Michael Stay's article ZIP Attacks with Reduced Known Plaintext section 2.1

[BK94] throws away six bits in key1₇. By using them, we can reduce the plaintext
requirement to twelve bytes at the cost of increasing the work factor by four

The 7-contiguous-bytes attack variant would be approximately 4 times slower than the 8-contiguous-bytes variant currently implemented.

When only 7 contiguous bytes are known, that would be a huge speedup compared to bruteforcing a full byte to reach 8 bytes and apply the 8-bytes variant. (256 / 4 = 64 times faster)