Craig:
The short answer is you can't stretch this object (DET_Batt_Insulation SE9) because it was not written to be stretchable.
The longer answer is that the width & length dimensions are not set via the A & B variables, but from the R-Value and Length parameters, which are not stretchy. Then this library part is actually calling one of nine other library parts (which just have 2D symbols, no 2D script) of the specific size specified by these parameters rather than drawing the insulation using the 2D Script of the part.
So it is not a problem on your end, this is how this object works.
HTH
David