Hi. Thanks for helping make CircuitPython better! In this case, though, I think the documentation is correct even though it looks unusual.

Here's how the C code defines the way that TileGrid's constructor needs to be used:

    static const mp_arg_t allowed_args[] = {
        { MP_QSTR_bitmap, MP_ARG_REQUIRED | MP_ARG_OBJ },
        { MP_QSTR_pixel_shader, MP_ARG_OBJ | MP_ARG_KW_ONLY | MP_ARG_REQUIRED },
        { MP_QSTR_width, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 1} },

Notice that the line for pixel_shader is KW_ONLY and REQUIRED.

A "*", followed by an argument without a default value, is the same way you define such an argument in CPython3:

>>> def f(x, *, y, z=0): pass
>>> f(1)
TypeError: f() missing 1 required keyword-only argument: 'y'

Let me know if I overlooked something and thanks again!