I'm not sure if the limitation is in how Spotify streams audio to the add-on, or how the add-on handles and presents audio to Kodi. The original add-on author is long absent from the forum so the add-on is essentially unmaintained these days; we manage to unbreak it occasionally but if new features and changes are desired, the responsibilty for making them rests with the requestor.
NB: I personally stopped using LibreSpot some time ago as the iPhone app that I normally stream from evolved to support AirPlay and Kodi shows up as an AirPlay target. In this arrangement the current-playing track duration of the media shows correctly. I haven't tried the lyrics add-on (most of what I stream doesn't have lyrics) but since 'time' is correct I think it would work.