DD guy here. This is the most plausible explanation.

When you're under LOI there is a lot of back and forth, which ultimately guide how the purchase agreement gets formulated. So if this was the case, then they would have made the trade off of "ok she's not letting us see the list, but we'll make sure the SPA is ironclad about this". Ultimately deals then get some money locked into escrow or RWI to soften the blow of the cost implication.

At the end of the day, let's say you're JPMC and the company that you acquired did exactly what Javice did. You have an SPA that binds you legally (meaning, if they caught lying post close, they'll get sued), how on earth would you think someone was dumb enough to try to get through diligence, then operate the company post close, and NOT expect to be found committing fraud.