"Romantic shadow-hunting": The Plantation of Ulster

There are people who like to rewrite history. I don't mind that when missing pieces are put back into the jigsaw, but when things are just made up with little or no basis in fact then my toes curl up. One of these is the idea that the Plantation period which brought large numbers of Scots to Ulster was actually a kind of "homecoming" - because these people were probably descended from some ancient obscure, unrecorded, largely speculative tribe who had migrated from Ireland to Scotland thousands of years previously. Here's a quote I stumbled upon recently:

"...may I say that the effort to prove that the Scots who came to Ulster in plantation days were really Gaels returning home after centuries of sojourning abroad is just romantic shadow-hunting. The thesis that "the Ulster-Scot is largely of Celtic origin", if it means anything at all, is without historical significance..."
by Prof TW Moody FTCD, The Ulster Scots in Colonial and Revolutionary America, 1944 (published in Studies - an Irish Quarterly Review, March 1945)

I can't see any problem with an entirely justifiable, well recorded, large-scale 1600s migration of Lowland Scottish Presbyterians (and of course English people too) - without the need to backwards-engineer some mythical, unknowable, mystical pre-history into the equation.