I bet it's hard to render realistic trees in a piece of hardwood.
Actually it is easier, ...... when using hardwood, ...... but it has to be a "tight" grained hardwood, ...... and surely not Oak as you suggested, to wit:
It's some kind of heavy wood, maybe Oak?
The grain of Oak, Chestnut, and probably Ash is far too large for intricate carving.
Maple, Cherry, Black Walnut, Teak, Ebony, Beech, Birch are "tight" grained hardwoods and surely excellent woods for "carving". (think of walnut gunstocks)
Softwoods such as the conifers, balsa, Linden (Basswood) are great for carving ..... but not so great for intricate work or longivity due to them being subject to abrasion.