Yep, physically moving a woofer about 8 inches from a planar loudspeaker causes a time differential between the two equal to a 0.6ms delay (sound travels at 343 meters per second, or 0.343 meters per ms). Is Bruce’s recommendation for the woofer to be delayed behind the LFT panel, or visa versa? I suspect the former.
By the way, the plate amp included with the Rythmik Audio/GR Research OB/Dipole Sub includes a Phase/Delay control, continuously variable from 0 to 16ms (0 to 180 degrees). That allows one to position the OB woofer for best room response, using the Phase control to align the woofer with the panels. That is accomplished in the analogue domain, no digital conversion.
Having separate midrange and tweeter drivers does NOT mean the ET LFT-8b/c is not a "true dipole." Magneplanars and other true dipoles also have separate bass, midrange, and tweeter drivers. Now the LFT-8b is not 100% dipole as it has a sealed box woofer. The LFT-8c is 100% dipole (front and rear firing woofers, opposite in polarity), but not open baffle like the Rythmik Audio/GR Research woofer.
Yes, changing the degree of toe-in affects the speaker/room interaction, but that is not necessarily a negative thing. For instance, with extreme toe-in---like the two LFT-8b/c panels positioned so that the back wave of each reflects first off the two side walls, that reflection reaching the wall behind the speakers where it is then reflected again. The time taken for the back wave to reach the listening position is thereby increased in time, potentially a good thing. It’s like having the speakers further away from the wall behind them. 3’ is the most common recommendation, but 5’ is better. That creates a 10ms delay between the front and back waves, which the brain interprets as two separate sounds, rather than the rear wave being a smearing of the front wave (a minimum of 10ms between the two sounds is required to achieve that).