heh, never heard that claim...
for me, the Holy Roman Empire can be divided into 2 general periods, further subdivided into more. those 2 general periods were the unified Empires 800 to mid 1200s (end of Hohenstauffen rule), which is further subdivided into the Frankish and the German periods. and the second general period, the period of fragmentation (Interregnum onwards) which i subdivide into three smaller periods, the first from Interregnum to the Augsburg religious peace (loss of central authority), the second from the Augsburg religious peace until the westphalian peace 1648 (loss of religious unity), and the third from 1648 to the end 1806 (loss of political unity).