That does seem like the obvious argument, but...
Technically, storing chat history from 24 hours isn't really any different than storing it for 30 days. Or 30 years. Either it's on disk somewhere or it isn't, and if it is, then you can just...not delete it. The option to not delete it may not be exposed in the 24 hour option, while it is in the 30 day option, but courts tend to be skeptical of arguments of the form "we have carefully engineered this machine not to have a button to make it follow the law, thus we are blameless".
And of course, even if it really is difficult (obviously it's not impossible given Google's resources and that this is a Google created tool!) to stop deleting the 24 hour chats, Google had other options. For example, they could make a good faith effort to ensure that critical chats took place in channels or group chats where the history setting was enabled. But instead it seems they made an effort to move chats away from there.
> where would cause irreparable damage to the common offering both internally and externally.
I think you'll find that "being able to comply with the law" is generally seen as a positive. It's actually a feature that Google touts quite highly in the contrext of Google Workspace. :)
Also note that this is something that was totally supported by their chat platform when history was enabled, and if you read the PDF, a constant theme is people upset because they were being forced to avoid newer features (like threads) because you couldn't make it delete chats that should be preserved if you were using threads. So rather than the legal system asking Google to damage their offering by adding a feature to it, we see Google asking staff to use a less capable offering because it was lacking the feature.
It is certainly possible that a court may find that what Google did here is okay; that they didn't have an obligation to either not delete relevant conversations that took place in the channels with extended history disabled or hold those conversations in channels with extended history enabled.
But...I wouldn't bet on it. And note that this also came up with the Musk/Twitter saga:
> In McCormick’s letter today, she says she believes Musk did use Signal. “I am forced to conclude that it is likely Defendant’s custodians permitted the automatic deletion of responsive Signal communications between them and possibly others, and that those communications are irretrievably lost,” she writes. Twitter has requested sanctions against Musk, but McCormick hasn’t decided on whether she’ll sanction him yet.
(Source: https://www.theverge.com/2022/10/5/23389568/musk-twitter-sig...)
Musk responded by folding and aggreeing to purchase Twitter after all. And although there were a number of factors there (his case was horrible) a decent chunk was his usage of automatically deleting Signal chats for communications he had an obligation to retain. And whether or not this was okay wasn't ever really an open question; the questions were whether it happened, and if so, what sort of penalties Musk would have to suffer.
> It would be a large precedent.
Not so much.