Definitely, longer lines is a must indeed.
But it stil requires a light "not normal" kite when under 10 knots, and then with longer lines you can push the limit down even further
I use 26 m for my small kites 3.5 and 5 and up (dislike 21-22 m even for these, when hydrofoiling), and then when a 12 m2 light kite (got the Zeeko Notus Air) becomes on the low side I change up to 31 m, huge difference.
Longer and it becomes not much fun to carve and make fast transitions, and very impractical, so I personally stop there.
So having 2 bars with different line sets it is always easy to change or select, having 3 would be a hassle (eventhough I got my 21 m for waveriding, but never use it anymore for foiling).
I hardly ever use the long lines with kites under 10 m2, does not make much sense - only in rare cases where the wind is VERY up and down, it works well with say a 9 m2 - as you dont get more power with the long ones, you can just fly more power when starting and turning/carving.
Using 32 m with my 11 m2 foilkite when its 5-7 knots, and change to a 12 m2 onestrut when it hits 7 knots in 10 m height
But below 9-10 knots you need a light kite, no matter what - you can sometimes get away riding with a normal kite and long lines in 9 knots indeed, but because of the risk of it dropping, and the difficulty getting out in onshore winds, almost or impossible, it is not worth using these IMO if you can get a lighter one.