

144hr TMOV 2yr window?
My parents (US passport) traveled to Beijing in early 2014 on L visa and stayed in airbnb property for first two days before checking in to hotel for the next few weeks but I have gut feeling airbnb host didn't register them with local PSB as requested prior to arrival. They are now planning to visit Shanghai this Summer for 5 days and want to do the 144hr TWOV enroute to Hong Kong.
I saw this new information from EEA dated Jan 18, 2018. I used Google translate to try to read it in English => "(d) within two years of violating the registration of accommodation and the circumstances are serious".
My questions are:
1. Since I'm pretty sure airbnb host back in 2014 didn't register them with local police station, what is considered "serious" condition to be denied 144hr TWOV by immigration agent? My parents didn't intentionally try to not register within first 24hrs since their second night was checking into hotel that automatically register them for the remainder of their trip.
2. Can we assume the 2 year timeframe surpassed back in 2016(trip was in early 2014)?