Yep, you are right about the 6 digits, my error. I was counting the Area code as a two digit number (like 01 or 00)... ;-)The 780 looks at the system sub-audible, but also uses the repeaters ID number that is not included in the displayed data used by the PRO-92/2067. I you had a PRO92/2067 to search with, you could wait until a talkgroup came up and then note the frequency in use as well as the "home repeater" number within your talkgroup to be able to tell what the repeater number is that particular. Not too bad to figure out if you have a three frequency system I guess.
My guess as to the reason the 780 uses this method is that it would be patent infringment on the GRE method of LTR tracking.
LTR frequency.
True the PRO-92/2067 does not need the order of frequencies, but the 780 does.