Hey, thanks for the heads up. This is one is a little tricky, we’ve been considering a few options, either by simply changing it to the kun’yomi reading or by adding words that use the on’yomi like 爪楊枝 but we’ve not settled on anything just yet. We’ll keep you in the loop and let you know what we decide eventually.
Update: There may be some more changes in the future but for now we decided to change the primary reading to kun’yomi, added し to the warning list, and updated the reading mnemonic and hint.