As if you don't recall, the last true mega-leg was in TAR 10.
There was also TAR14!
A little different since teams had to find Phil at the Mat in the middle while for this Mega Leg, it might be just teams Racing all day with no Mat.
It may be similar though since in TAR14, they didn't have any rest and continued Racing all in Beijing.
Something big about the mega leg: most KOR legs have some spot where the teams can rest. This leg seems like 0 rest whatsoever
That might be the distinction. Since both "halves" of the Leg will be in Hyderabad, it'll be a long day with no plane or train ride between the two halves (like TAR10) or the overnight rest in the stadium on TAR8.
All in all, the Mega Leg isn't necessarily something "new" or something we haven't seen before in various forms on the Race.