Extra true in the output log when a language server disconnects

[ogoffart]

This is quite a minor issue and I don't even know if that's the right repository to report this "bug", but there is an extra true in the output when a language server disconnects, and it looks messy in the log.
It looks like this:

[Info  - 9:24:48 AM] Connection to server got closed. Server will restart.
true

Looking for the text in an internet search shows that this extra "true" is present for most language server. (As paste the debug output in their bug report). They all have the extra "true".
dart-lang/sdk#54441
Exafunction/codeium.vim#403
scalameta/metals-vscode#1509
slint-ui/slint#4619
swiftlang/sourcekit-lsp#1521 (comment)
nim-lang/langserver#207
DetachHead/basedpyright#592
(... and many more)
Although one can also find a few occurrences of "false"
microsoft/vscode-java-debug#1421
redhat-developer/vscode-java#2756 (comment)

I couldn't figure out easily where this bool output output come from.