Flash memory fragments just like normal storage. The only difference is that a flash chip has the same exact read speed, regardless of fragmentation. However, a flash chip suffers from decreasing write speeds as fragmentation gets worse and worse. (I also hate how the modern flash chips take control of the wear leveling from the OS, and do it themselves, which made trying to use a defragmentation program on a flash chip almost entirely guaranteed to at best not make the situation any better, and typically makes it worse)