Heres my hypothesis for this. When he was playing in Macau recently he def played with hurricane on the forehand.
In the beginning of the german season he experienced some difficulties and losing to players he def shouldn't lose to. It might have been because hes adjusting or something like that. But i think it might have something to do with the temperature, in german its much colder which makes the rubber significantly harder. When he plays in china where the temperature usually is higher the hard rubbers are easier to hit through and thats also what he is used to. He have played for Shanghai where its substantially hotter also during the winter. And playing in Macau is also a lot warmer than in Saarbrucken.
I get that the temperature of the venue probably is regulated, it will still be different.
I have experinced something similar where the H3N is a lot harder to play through in colder venues in the winter compared to the very hot venues in the summer.