Most PhD have a few papers before finishing the dissertation. Many times the dissertation is made of a few paper by the author glued together. The papers usually chain, so it's instead of

introduction1 -> main1 -> conclussion1

introduction2 -> main2 -> conclussion2

introduction3 -> main3 -> conclussion3

the thesis is something like

long introduction -> easy example -> main1 -> main2 -> main3 -> main of preprint -> long conclussion

Thesis by publication is only one way, and not even the most common in many fields. I can't access the actual text of this thesis, but the abstract sounds more like a monograph and I don't see any author publications before the thesis that would lead me to think otherwise.