It's a little more nuanced than that imho. The club were under no obligation (I think) to provide third party information to the investigation, but everyone knows such information exists because it was (partly, I suppose) provided at CAS. So by deliberately not providing information they have previously been able to provide, they were being obstructive.
I am not surprised the club did that and I am not surprised the PL included the allegations. Nor would I be surprised if the panel found in favour of the PL on this issue, as CAS did for UEFA, although maybe the Leicester decision makes that less likely due to the wording of the rule (and the later guidance) on disclosure.
But, like I keep saying, what do I know? :)