powerdisp as evflag?



Is there a commonly met  reason which explains why
I can't use powerdisp in evflag mode?

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(%i1) display2d:false$
(%i2) e : 3*eps^2*(3*r^4+24*q^2*r^2+8*q^4)+3*eps^2*cos(4*g)*r^4
                                      +24*eps^2*cos(3*g)*q*r^3
                                      +24*eps^2*cos(g)*q*r*(3*r^2+4*q^2)
                                      +12*eps^2*cos(2*g)*r^2*(r^2+6*q^2)
                                      +4*eps*(r^2+2*q^2)+4*eps*cos(2*g)*r^2
                                      +16*eps*cos(g)*q*r+1 $
(%i3) powerdisp;
(%o3) false
(%i4) (powerdisp:true, collectterms (e,eps));
(%o4) 1+eps*(16*cos(g)*q*r+4*cos(2*g)*r^2+4*(2*q^2+r^2))
       +eps^2*(12*cos(2*g)*r^2*(6*q^2+r^2)+24*cos(g)*q*r*(4*q^2+3*r^2)
                                          +24*cos(3*g)*q*r^3+3*cos(4*g)*r^4
                                          +3*(8*q^4+24*q^2*r^2+3*r^4))
(%i5) powerdisp:false$
(%i6) properties (powerdisp);
(%o6) ["system value"]
(%i7) declare (powerdisp, evflag)$
(%i8) properties (powerdisp);
(%o8) ["system value",evflag]
(%i9) ev ( collectterms (e,eps), powerdisp);
(%o9) eps^2*(3*(3*r^4+24*q^2*r^2+8*q^4)+3*cos(4*g)*r^4+24*cos(3*g)*q*r^3
                                       +24*cos(g)*q*r*(3*r^2+4*q^2)
                                       +12*cos(2*g)*r^2*(r^2+6*q^2))
       +eps*(4*(r^2+2*q^2)+4*cos(2*g)*r^2+16*cos(g)*q*r)+1
(%i10) ev ( collectterms (e,eps), powerdisp:true);
(%o10) eps^2*(3*(3*r^4+24*q^2*r^2+8*q^4)+3*cos(4*g)*r^4+24*cos(3*g)*q*r^3
                                        +24*cos(g)*q*r*(3*r^2+4*q^2)
                                        +12*cos(2*g)*r^2*(r^2+6*q^2))
        +eps*(4*(r^2+2*q^2)+4*cos(2*g)*r^2+16*cos(g)*q*r)+1
(%i11) 
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Thanks in Advance,
Ted Woollett