highly conductive layer

Hi,

I tried to do a simple transient heat transfer model as follows:
one model with a thin solid domain on top of a thick domain and
another model with highly conductive layer on thick domain.

The thickness in the highly conductive layer in the 2nd model is same as that of thin solid domain of 1st model.
I used anisotropic thermal conductivity property for the highly conductive layer and for the tin domain: K=[1700W/m*K,1700W/m*K,8W/m*K]

I noticed that the result in thin domain do not match. The highly conductive layer provides a peak temperature significantly lower.

Question: Does the highly conductive layer model only works for the isotropic material only?

Regards,
Susant