What is capacitive thermal compound

[xYowie]

According to arctic silvers website arctic silver 5 is not conductive but slightly capacitive, what does that mean?

 

[clutchc]

I take that as meaning it has a very weak form of electrical conductivity. Meaning (IMO) it is not safe to assume it is 100% non-electrically conductive. Like capacitors, slightly capacitive indicates it can retain a charge. Might it discharge as well? After all, it contains silver, one of the most conductive metals.
I use MX-4 and find it has the same thermal conductivity as AS5 and is not electrically conductive.