but I believe this also overrides the 3us power-on-reset delay described here (unless I copy all of that, too):

https://github.com/amaranth-lang/amaranth/blob/main/amaranth/vendor/_siliconblue.py#L350

However `default_rst` is ORed with the delayed POR:

> If the board includes a dedicated reset line, this line is ORed with the power on reset.