Question: Maple does not support symbolic matrix for Grammians?

I am really baffled by this. I was starting to think Maple control system is good, only to find I get an error when I try to obtain the controllability Gammian for a state space system which is time varying.  Maple only seem to support a non-time varying A,B,C,D for this function.  Can someone please confirm this, or may be I am doing something wrong?

I was trying to verify my hand solution for a HW using Maple.

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restart:
alias(DS=DynamicSystems):
A:=Matrix( [[2,-exp(t)],[exp(-t),1]]);
B:=Matrix([[0],[1]]);
sys:=DS:-StateSpace(A,B);  #created OK
m:=DS:-Grammians(sys);

Error, (in DynamicSystems:-Grammians) symbolic value(s) in model: t, exp(t), exp(-t)
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If the system is time invariant, then it works. Example from help:

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restart:
alias(DS=DynamicSystems):
aSys := DS:-StateSpace( <<-5,3>|<3,-4>>, <<2,3>>, <<1,0>|<0,1>>, <<0,0>> ):
m:=DS:-Grammians(aSys);
---------------------------------

The main advantage of using computer algebra system for control system is to be able to do things using symbolic which is much more powerful than just numerical computation as with Matlab. There is nothing in the above linked to help page that says Maple does not support time varying state space for this function (unless I missed it).

Is it possible to add support for LTV in Maple 19?

ps. note that the ControllabilityMatrix works on LTV:

m:=DS:-ControllabilityMatrix(sys); #OK

But I wanted the Grammian.