Burying the graft union with a dwarfing stock should produce a larger tree than not burying the union. For a larger semi-dwarf, it may not make much of a difference but won't hurt as long as the rootstock isn't buried too deep.
To Sandbur's point, standard or full size is based on the variety's potential. A natural dwarf (low vigor) variety will still make a small tree on standard/full-size rootstocks. For such a tree, burying the graft union won't help or hurt. If it were on a dwarfing rootstock, buring the graft union probably helps a little but it still will be a small mature tree.