We saw something similar recently with the leak of the SCOTUS Roe v Wade opinion. There was a huge push to move the discussion from how controversial the opinion was & what the fallout would be towards "leaks are bad & we have to find who did this".
Agreed; but…
In your example, it’s both. In that case, it’s a completely legal and expected part of the process for the justices to decide things, even if it’s things you don’t like.
In the case of Snowden or Manning or others, they were leaking something that the government says it does not do, should not do, and expressly illegal things.
So it’s not a great example. While we likely agree on abortion; Roe has always been on “shakey legal ground” (RBG’s words) and the 7 justices that decided it could not agree if it was because of the 9th or 14th amendments, and offered no explanation how one or both of these superseded the 10th in this scenario. If you haven’t, read the full opinion, do, it gives insight into what is going on… legally anyhow.
So as to your example, it wasn’t a whistleblower or shooting the messenger to find the scotus leaker - it’s literally protecting the sanctity of that institution’s process.
If you can’t imagine a scenario you would be upset a decision you agreed with was leaked in order to bully justices or influence a coming election, you aren’t thinking hard enough.