The ED manual says ( page 308 ): 
"Hook Mode (TAG: OWN, BULL, or CURS), rotary OSB 18. This OSB function is only displayed when you have hooked a TAD symbol with the cursor. TAD symbols can include the SPI, TGP diamond, waypoint/steerpoint, or bullseye. When a symbol is hooked, the SPI symbol is placed over it and a dashed, yellow line leads from the SPI symbol to the rotary selection."   
Someone could help and clarify if is it to intend as a bug or is the normal behaviour ? 
Thanks.