I noticed the same thing. I'm glad I'm not the only one. Not sure if it is a bug or a feature though.Does the new Safari Tab groups NOT save when quitting Safari? I made quick organization of all my tabs only to find they're all gone after relaunching Safari Tech Preview this morning. Serious WTF, not what I would expect. Safari is set t relaunch all tabs and windows from previous session. This better be a bug, not a design choice.
Also, pinned tabs do not show up in Tab Groups. What is the point of a Pinned tab if its not always there?