No-one seems to have mentioned it yet, but it’s been suggested that like Pentre Ifan, the outline of the capstone seems to mimic the outline of Carn Ingli behind the monument. Kammer’s photo here
themodernantiquarian.com/post/8128/images/llechytripedd.html
might convince you.
Perhaps local awareness is the source of Merrick’s folklore – that St Samson threw the stones from Carn Ingli.
(this idea is suggested in ch6 of Alasdair Whittle’s ‘The Archaeology of People’ (2003))