I hope its a rule of thumb. If level 10 is Beta level (I did not know about the full scale, with Iota etc, until this thread prompted research), then the powers are not powerful enough to reflect the level. I think scale wise the 1-10 Scale is the Iota, Theta, Eta, Zeta, Epsilon range.
Leave the Delta and higher levels to be Ascension-esqe and big bads with big bad powers.
It helps to know as a frame of reference what type of power level is in the 1-10 Scale.