The line change at Do Lung Bridge was introduced in the Redux cut in 2001; probably an alternate ADR take. It was likely due to the additional scenes during that sequence where Willard is actually looking for fuel. The alternate line was also kept for the Final Cut.
Current digital versions of...
The Original/Redux Blu in the US/UK set has all those audio tracks, too (though the video encoding/compression is abysmal). With all that, I'm not sure why they couldn't have slapped that restored original 5.1 on the UHD, too.
It just has the Atmos remix, which honestly doesn't seem that different to me from the "original theatrical" 5.1 on the BD (but I only have a 5.1 setup). Although, there is one line of dialogue from the Redux version that incorrectly pops up in the theatrical, probably due to a branching error...
All three cuts are from the same 4K remaster, which looks fantastic on the UHD discs. But the standard Blu-rays (especially the Theatrical/Redux disc) are hobbled by poor compression.
Most likely a branching error. It probably got missed during the preparation of the branching points for the original Blu-ray and was then grandfathered into the new one.
It's a small thing, but definitely annoying.