DNA is more complicated than that. I don't fully understand the process, but I believe it works like this:

You can't read the atoms in DNA one after the other and make a list. You chop the DNA into pieces and pattern match sections (fragments) against markers. Then you try to put fragments together by matching overlaps.

But if you have sections that repeat, or have a lot of the same atom over and over, you can't directly read those.

Usually when they say: "we published the DNA" they mean the "coding section" - those are the sections that can make proteins. But there is a lot more to DNA, non-coding, or junk DNA that can not be easily (or at all?) read.

So for the comment above yours, I think what they have is fragments, but no overlapping sections, so that can't put it together into a whole. It's not like a file with gaps - it's random pieces of it, of random lengths, in a random order.