[dataflow]

Not a lawyer, but my amateur guess is the answer to your first question would be yes, and the answer to your second question would be no, because of the common-sense understanding of how computer storage works and what it means to delete something. There's no need to have an information-theoretic definition of "destruction" here.

[squirtle24]

Relevant law cited elsewhere in the thread: "(e) Failure to Preserve Electronically Stored Information. If electronically stored information that should have been preserved in the anticipation or conduct of litigation is lost because a party failed to take reasonable steps to preserve it, and it cannot be restored or replaced through additional discovery, the court ..."

The key word is "reasonable", which is what the court must decide happened here. OTOH deliberately enabling "history off" doesn't sound like a reasonable steps to preserve records under legal hold. Having said that, I wonder if it also means voip/video calls must be recorded, especially if the feature is available in whatever app they use. Further, even if they use a purpose built "off the record" app, deliberately choosing to use such an app could be argued as failure to reasonably preserve records, if a regular history-preserving app is available. So I think the answer to my first question could be a no.

[dataflow]

The key word to me is "stored". The common-sense definition of storage refers to non-volatile storage, not RAM or data in transit.