just reading it smeels like baloney... if bus parking was really the problem it would have affected alot more pci hardware, second if I understand bus parking it's optional in the PCI 2.1 inplementation. If for example the SBLive was created with a requirement of bus parking then that means that Creative would have made a card that was no PCI 2.1 compliant.
My take is that some hardware was made with bus parking as a requirement and others as optional. If the chipset does not have built-in bus parking then it's included in the hardware, somehow I take it that the hardware was created without bus parking and was relying on the chipset to provide it. In any case it doesnt matter since it was fixed in a driver upgrade.