Nothing REQUIRES redisclosure ever except a rate lock.
Our rule of thumb here is to only redislose if we need to capture an increase in a fee or if there is a new fee. Of course, you always have to have a valid CC driving the change and you must redisclose within 3 days of learning of that circumstance.
The GFE only has to do with the cost of getting the loan, not the costs of getting the home.
Who is paying what also has no effect on the GFE. The Reg dictates what must be shown on it.
I'm assuming the lot line issue was not known at the time of the first disclosure so it wouldn't have been on the original GFE. Honestly, I don't think it should be a charge to the borrower at all. It should show on the Seller's side of the HUD because they cannot sell a non-conforming parcel.