Yeah, I don't think the specific reason for that sentence in the manpage applies here. But the general sentiment is correct: not all programs support `--` as a delimiter between arguments and inputs, so many xargs invocations are one argument injection away from arbitrary code execution.

(This is traditionally a non-issue, since the whole point is to execute code. So this isn't xargs' fault so much as it's the undying problem of tools being reused across privilege contexts.)