Once had a crumble where cumin was put in instwad of cinnamon due to some careless spice jar selection. Thankfully such a small amount was put in it only tasted odd rather than inedible.
@keith rhubarb is still amazing… unless you have the tinned stuff, in which case you have my sympathy.
@slicky think you could test if a custard crumble works? I would be interested in this research.