Defrag Freespace

What does Defrag Freespace mean, is there anything to defrag in Freespace,

I observed defrag does not place all used clusters together, and Freespace clusters together,why

What does Defrag Freespace mean, is there anything to defrag in Freespace,

I observed defrag does not place all used clusters together, and Freespace clusters together,why

Read Defragmenting free space

In Defraggler ➢ Analyze ➢ View files what is listed after you defrag?

Thanks !!! bit misleading below,

Which option should you use? If you want your freespace to be as defragmented as possible, choose Defrag Freespace (Allow fragmentation). If you want to reduce the amount of fragmentation in your current files, choose Defrag Freespace

I would have thought correct term for full defrag of freespace should be Defrag Freespace and not (Allow fragmentation)