Unfortunately, since few or no Gaels were musically literate, the music for these competitions was written by outsiders, and the performances were judged by outsiders. It takes a long, long time to learn about a different musical tradition. Scales and rhythms were adapted to the well-tempered Western European norm. They probably decided that deviations from this were just native errors. Grace notes are a personal thing and Lewis singers tend to use more than most, but unless you were trying to copy a piobaireachd exactly, grace notes are entirely up to the individual in Scots Gaelic singing - a complete contrast to Irish Gaelic singing where they seem far more widespread.
Work songs are very rare in Irish singing.
The svarabhakti also exists in Italian. Assume your audience knows Gaelic, even if they don't. Therefore you have to be authentic in your pronunciation and respect the stresses and syllable lengths of the words despite what the music says. The Rankin Family on the other hand do not. I suspect the Rankins would sell fewer records if more people spoke Gaelic.