When a track is short of horses in a class it can be done. Especially now with the longer time between draw and race. Usually done when a horse is in where it can win and enters back in a couple days to race back in that class. “Eligible when entered”.
I've seen one horse (and others) listed multiple times on the same card as well as consecutive days of the same week, but often times as AE's (Also Eligible's).
Your reason for the most part. Sometimes they are stake races too that the trainer nominated, entered and fees paid in multiple scheduled to race simultaneously with the hope they get chosen for at least one!
If they actually raced and are racing back quickly try to get a hold of lifetime past performances to see if they've done that with the same trainer before, and the outcome, they might of had consistent success at times.