The lock screen stops repeating the key that woke it
Waking a blanked lock screen could type the wake key over and over, so the password field was already full of dots. Pull request 7806 drops that repeat.
A slow display can stall the compositor while it modesets. The key's release arrives only after that stall, and the field repeats the character the whole time. The pull request cites an Apple Studio Display taking 2 to 4 seconds.
The field now ignores auto-repeat on letters. Backspace and Delete still repeat, and Escape or Ctrl+U still clears the field. The GitHub user berndb opened pull request 7806, and David Heinemeier Hansson merged it.