I had not noticed this until listening to Peter McCalister playing “The Red Speckled Bull” (PS 237) at the MacDonald Cuach this year (2019).
There are three different rhythmic styles for fosgailte crunluaths in the MacDonald collection. (All of them are open, of course.)
The first is rhythmically familiar, a style we play today: Compound first note held long, internal note short.
But the second style is quite different: first and internal notes are of equal value. (Peter chose to play his in this fashion.)
And there is yet another style, one quite fascinating: the first note is cut, and the internal note is held.
Once again, it seems the ancients surprise us with their variability and breadth of musical options.