Yep. One end connected makes it a capacitor. Same effect you get with shielded cable. The shield presents a capacitance to ground because of it's proximity to the conductor. I don't think anyone would argue that or the similarity in the circuits. Both ends disconnected from the secondary coil eliminates the problem BUT FOR ONE THING!!! If you shield an inductor with copper (grounded or not!) it changes the performance. I can't say why because I don't have the tech chops, but I can assure you that it does because of my own experience shielding pickup coils with copper tape. Copper has a unique ability to bend EMF and I have to assume it's this property that is responsible.