Yes, Indiana Jones and the Great Circle actually has not only an Ultra preset, but also a Giga and a Hyper preset - the latter is the maximum. The actual graphics options between Ultra and Hyper are the same except for the anisotropic filtering, the latter only increases from 8× to 16×. What's actually changing with Giga and Hyper is the texture pool size, which has long been a quirk of the id-Tech engine.
So reserved and presumably the game allocates a fixed amount of graphics card memory (the “pool”) and if this size is not enough, the game stutters. It doesn't matter whether that much VRAM is actually needed at the time, which has the disadvantage that the game sometimes runs worse than it theoretically could when there is a shortage of memory, but has the advantage that the memory allocation and occupancy while playing is so good like not changed. So if the graphics card memory is enough at the beginning of a game, it will probably also be sufficient at the end.
Unfortunately, it is virtually impossible to say how much VRAM the game really needs. The game allocates around 14 GB in the benchmark with the Hyper preset, 13 GB with Giga and a little more than 12 GB with Ultra - so the differences are small. With a 16 GB graphics card, there were no problems with the Hyper preset in Ultra HD, even after playing for a long time. It is unclear whether this also applies to a 12 GB graphics card.
