Stolen phone doesn't look different from a legit one, you need to actively verify its record. I doubt an insider tip can be honestly mistaken for a legit one.
Which makes the plausible deniability even weaker.
You might have a tip about a merger because a PI is watching a corporate parking lot. Just because something is a secret, doesn't mean an insider leak is the only way for it to be known.
Which makes the plausible deniability even weaker.