It's grafted, most likely a Bloodgood. Will always have long internodes.
Why do you say it's grafted? It's a Acer Palma dwarf Japanese maple. 'Babe's Dwarf'. It's at a tree nursery not a bonsai shopIt looks grafted, you might want to pass on this unless you know how to deal with it.
Every tree nursery I go to has all grafted JM. The roots are always the more hardier regular green while the trunks are some fancy cultivar.It's at a tree nursery not a bonsai shop