I need input on whether or not matches on my Mom's Irish side are IBS or IBD.

Here's the story.

My Mom has a predicted second cousin match (Don). His longest segment with her is 95 cMs on chromosome 12. Don is on ancestry and GEDmatch but not FTDNA.

ON GEDmatch, both Don and Mom match many others on part of this segment (9 to 16 cMs). All of these matches match each other on this segment.

One such match (Mary) (16 cM) is also on FTDNA as a predicted 3rd - 5th cousin to Mom. On FTDNA, she and my Mom match another group of people on chromosome 12. This segment partially or completely overlaps the one on GEDmatch. And all of these people match almost of the others per the FTDNA matrix. (I assume that the few cases of non matches fail to meet FTDNA's 20 cM match benchmark.)

Overall, I now have 26 people lined up on Mom's chromosome 12 in Genome Mate not counting Don, Mary or Mom.

Ancestry clearly considers this a pileup segment since the two matches shared by Mom and Don on ancestry disappeared in V2.

I had always thought that pileup segments consisted of many people who DID NOT match each other. This is not the case here.

Obviously I know to continue to explore Mom's connection with Don and Mary. (This is not productive thus far). However, I'm not sure what to do with these other 26 people. Would I be tilting at windmills to investigate further?

Input welcomed, please!