The string-thru is after-market amd was most likely added together with the three point because that was only introduced in 1973, the earlier Triumphs still had the two point. Unsurprisingly, the then-owner must have been dissatisfied with this wonderful, string-pull-resistant work of American engineering which justly
has so many vocal fans here.
And as he mounted the three point, he must have thought of the string-thru too, possibly because the first three-points came out with the early Rippers and had that too (though some of the Ripper prototypes did not). Considering that an E string on a short scale has less tension and hence also less saddle pressure, the string-thru is a good idea.
I like the cherry refin btw!
Uwe