Hi Danny, yeah that is how Inset is intended to work - it's related to offsetting of the surrounding surfaces, so the result kind of takes on the shape of the surrounding pieces.

So for example a starting piece like this:



Will produce a protrusion like this where the protruded shape has the same angle from the outermost pieces:



Also because Inset uses an offset of the surrounding pieces to form the shape, it allows for things like this:





If it instead tried to make a shape that went only like an extrusion in one fixed direction like you were thinking about, multi-face inset things like this would not really be possible, because there are multiple directions involved not just a single overall fixed direction.

- Michael