Apologies for the delayed response. Yes the Delock 90504 does in fact operate like a proper switch. It uses the Broadcom PEX8749 chip for it’s switching capabilities. When connected to 8x PCI-e lanes the device will simply be bandwidth limited but all 8x SFF-8643 Ports will remain operational.
Be aware that the Delock requires a firmware update from Broadcom to work correctly, I’ve attached a link to the forum post below.