What
When you combine two command-line options that both choose a remote backend, meaning where a session runs, the message is now built differently. It ends with "both select a remote backend; pick one." The leading "Error: " has been removed from the message text.
Why
The wording of these error messages has changed slightly.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not clear whether "Error: " is now added elsewhere, so the message you see may look the same.