Try any arbitrary command and it just works:

npx ejs file.ejs -o file.html --foo

This is only my second time using EJS, so perhaps this is intended behavior, but I believe most tools would emit a help warning. If it is intended behavior, then the actual use case that caused me to find this should perhaps be addressed in some other way. I was changing the delimiter and using

npx ejs file.ejs -m'|'

It took me two days to figure out that I needed a space after -m :(