Can I use 72 hours visa exeption for Guangzhou/Guangdong to do that?

Hey There
I plan to arrive to Guangzhou Airport, stay there one day, then take a train to Shenzhen and cross the border there. After that I have confirmed reservation to fly away from Hong Kong to Phillipines.
Is what you write here an official opinion of Chinese Visa Authorities? WHY 72 hour exemption for those 11 cities is not mentioned in official IATA TIMATIC rules for my country?
I have a POLISH passport.