Skips happen, if you compare abtirsi you see skips of even 10 generations or more sometimes between different versions of the same abtirsi.
They had descendants but only one branch survives, so you get these traditions where "had only one son, who had only one son" etc. The truth is that they didn't have only one son, but only one BRANCH still exists, all the other ones went extinct. These ancestors where no clans "meet" at are pointless to remember (since they are not relevant to common descent) and end up getting skipped except by some abtirsi who choose to remember them.
This is why abtirsi is an excellent tool for peering into the distant past but it isn't perfect. With the especially earlier ancestors it's difficult to say when they lived for instance. Did Samaale live 1400 years ago, or are the 9 Samaale the 9 surviving branches, but he lived 2000 years ago and 12-15 generations between each branch gets skipped?