The distance beyond Glideslope to me in a B777 seems to be of little use as there is no comparison from any manufacturer published value either in the AFM or Simplified Performance Charts.
I find the distance beyond G/S information useful as an awareness tool. The AFM landing distance data assumes a TCH of 50' and a G/S of 3 deg. The distance remaining after the G/S intercepts the runway surface would be approximately 1,000' less than than the declared landing distance available under those assumptions. (the G/S intercept would occur 1,000' beyond the threshold)
If I see a distance remaining after the G/S which is less than LDA minus 1,000', I consider it a warning that the AFM landing distance is optimistic for following the G/S to this runway. You might be using some of that 15 percent safety factor. This is a good time to make sure there is no extended flare if the LDR is very close to the LDA.
So together with the glideslope angle and the TCH, the runway remaining after the glideslope information can be useful in alerting one to a potentially surprising lack of runway remaining after touchdown. Especially nice to know when wind is variable and/or runway surface conditions are less than ideal.
I don't fly 777s, but that's not really important to the discussion. The same applies for any other transport category airplane with the same AFM landing distance assumptions. Airports like KMDW and KBUR have both had overrun accidents where an improved awareness of the situation may have been beneficial.
A 5,000' remaining after G/S note at a runway with an LDA of 6,500' would raise a red flag in mind if my AFM distance plus 15 percent safety factor was say 4,500'. Float for 3 seconds and it could be a little too close for comfort! With 6,500' minus 1,000, perhaps somewhat less so.