I have zero reason to spring to the defence of the Heritage Trust but to say "We know that some stones were selected for their distinctive appearances" is "a ridiculous statement" is completely unfair.
Nobody "knows" anything but there's enough evidence to say it may well be true and most people would probably think it was.
Alien landing strips are ridiculous, whereas this is just shorthand for "there is strong circumstantial evidence that". Anyway, come to think of it it IS true. Duloe.