In short, I think confusion arises over the need for a "conductive" enclosure for insulation tests, and a "non-conductive" enclosure for leakage tests of Class II equipment.
In the first case, the Rigel guides (and some other sources) do indeed mention the need to "wrap the enclosure in aluminium foil" and connect the flying lead to it ... but is seemingly silent in this regard for the second case (leakage tests).
I don't have to hand a current copy of the 62353 Standard, but hopefully someone may be able to tell us what it says about "foil" and so forth.
