No these bunkers are also seen in industrial or global age too. Its unlikely anyone could easily max out a museum artifact in those ages.
Sometimes they spawn hts faster than tank depots spawning usual tanks!
I sometimes encounter bases which have 3 bunkers. And all of them spawn hts every 10 sec. Worst of all they usually have the sally rides "spawn two machine gunner upgrade". Is this some parliament upgrade?
Redoubts can fight apcs or mass heavy(rarely seen in later ages) well. Motars can deal with British riflemen and field motar spam. Snipers deal with field motars and arty.
