Entry and exit stamps for ARC holders

The 1st time I entered on an APRC the girl at the counter (pre-egate days) looked at the card a few times and stamped my passport and I walked in. For some reason I glanced down at the passport and it was a round entry stamp instead of the usual octagon and said valid for 90 days…

So I went back to the counter and waited until she finished with the next person and said she’d given me the wrong stamp, she looked at it and said my ARC had expired which was why. She’d read the start date on the APRC as the expiry date of an ARC. Anyway she couldn’t change it so called a supervisor and I had to go to the main immigration office and have them go through everything there and cancel the 90 day visa and give me the right stamp.

I’ve wondered if I hadn’t noticed and gone back to the airport 6 months later to fly out would they have fixed it or would they have done me for overstay?

Purposely bait you then ban you from re entry???