Again, LPS is far to broad of a term for this disscusion.
For example, some commonly refered "LPS" corals and their natural locations;
Goniopora. ; stokesi freeliving on soft bottom, other attached to substrate
Fungia ; rubble or sandy bottoms
Polphyllia; most common on soft bottoms
Cynarina " found attached to rock substrates
Lobophyllia ; Upper reef slopes, hard substrate
Scolymia; reef slopes hard substrate
Symphyllia; reef slopes hard substrate
Caulastrea; sandy bottom
Trachphyllia; Sandy bottom
Catalaphyllia; soft bottom
Euphyllia; reef slopes hard substrate
Physagyra; Vertially in cave, hard substrate
Plerogyra; vertically in caves, hard substrate
Tubastraea ; Vertially and on cav roofs, hard substrate.
As you can see it varies tremendously, so, to say LPS need to be in the sand, is vary inaccurate, and shows the usefullness of terms like LPS and SPS.