This is exactly what I thought. Could it be that their results are confounded by a mix of rats for which the induced state of helplessness results in depression and some other rats for which this resulted in enlightenment of sorts.
I'm sure the researchers control for this. Most likely they block the rats' access to HN at the firewall, thus preventing them from ever hearing about stoicism in the first place.
Learned helplessness would manifest differently than stoicism. In LH you don't take clearly good (for external observer) opportunities because you believe it will all end badly anyway.
The stoic may have imperfect assesment of the opportunity's true value, but in LH the assesment is way more off - it's basically always zero for all opportunities.
> Research has found that a human's reaction to feeling a lack of control differs both between individuals and between situations. i.e. learned helplessness sometimes remains specific to one situation but at other times generalizes across situations.[6][8][9]