My guess is that it’s not a bug and WL considers a CD Track Splice Marker as just one marker rather than two as it technically is. So maybe I would call it an oversight and not a true bug.
I agree that it would be nice if WL could decouple a CD Track Splice Marker to be an end and a start marker for those that need to do that. Perhaps there is a top secret way or trick that PG or somebody else knows of.
The reason the first marker is getting converted is because that likely actually is a CD Track Start marker.