Sure, study up and develop this tree.
It is grafted. Cultivars or varieties are grafted onto some type of hardy rootstock. In the case of Japanese Maples it is usually the common green leaf type grown by seed. The reason for this is that cultivars, like Higasayama, Sango Kaku, Kiyo Hime, etc. will not be a true cultivar if grown by seed, the pollenator is unknown, and sometimes develop faster for the nursery trade (quicker plant to market results in less cost and more revenue). Therefore true cultivars are produced by methods like cuttings and grafting.
This graft is ok though. However you can get cutting grown plants which are considered to be better for bonsai training. Sometimes the junction between rootstock and scion is unattractive or grow at different rates. On the other hand sometimes nicely grafted trees are used.
Not criticizing this tree just trying to offer some info which is relevant to Japanese Maples and other plants that you'll encounter at regular nurseries. Remember that the trunk and roots are the most important elements when starting a bonsai and good stock has a better chance of a good outcome.
Have at it and enjoy yourself. Welcome to this hobby, art, obsession or sickness as applicable. Also, join a club for best results.
central MD 7a