Hi,
Other than Walt Disney being involved, I've heard that story many times also.
Another point is that the first steam locomotive Stevenson built had a gauge of 4' 8". It was later discovered that she stayed on the track better by widening the gauge to 4' 8.5"
Another point is that fractions were not well understood until relatively recently. The Annual RR commission reports from the Gainesville Midland RR the 1920's showed that the gauge was reported as 4' 8", 4' 8.5" and 4.9" from year to year. I doubt that the railroad was regauged every year, I think the secretary did not know how to write 1/2.
Another point of consideration are the locomotive order sheets from the 1870's-1890's. One reported an 0-4-0t where "t" was the representation for adding a tender (not today's accepted tank).
I also found a "ten wheeled locomotive" on an order form where further digging found it to be a 2-4-0 plus 4-wheel tender (sort of like the first D&RG locos).
It is very interesting researching historical records. It is not always easy not to put all of today's assumptions and standards into tinting the meaning of the old recordings. I am speaking from personal experience not scolding anyone.
Doug vV