The comment referred only to IP transfers, which are covered by the BTC spec. The more usual case of BTC-address to BTC-address transfers is secure over TOR.

TOR anonymity is usually overrated. It does secure you well for anything that doesn't interest the big agencies that much. If you've got something really evil to hide, using TOR is rather going to attract attention than the opposite. Many backbones and end nodes are intensively monitored and reveal a lot of useful information by statistical inference.