--flatutreexproofindex enables --noutreexo internally but it doesn't alert the user of doing so. When a user tries to enable --watchonlywallet it errors out and gives a confusing error message:
loadConfig: the --watchonlywallet requires the --noutreexo option off
--flatutreexproofindexenables--noutreexointernally but it doesn't alert the user of doing so. When a user tries to enable--watchonlywalletit errors out and gives a confusing error message: