A common mistake that some managers make is pushing the burdens of managing onto those you're managing. Any of us who have been managers can look back and see things that we tried to push down to those we've managed because it made it easier for us while later realizing that wasn't the best solution.

If there's a catch-all channel that employees are using to share knowledge that's not a bug, it's a feature. If, as a manager, you want a more structured means of conveying institutional knowledge generated within such channels then it's on you to put that together. Trying to push that burden down the chain often results in that institutional knowledge being shared verbally or via private emails/DMs in order to avoid the burden of documentation, which is a net negative.

Such information is a force multiplier for teams as well as a great asset for onboarding new hires. Both of those are direct benefits for the manager and the company, so take the advantage of that kind of spontaneous documentation rather than insisting on passing on the cognitive burden.