That seems odd to me. Every custom DTH I use does not run locally. Only ones that use the DTHs in the list I supplied do, including my Ecobee devices.
Homeseer have a delay not because of local processing but because of triple tap functionality. The switches wait to see if you will press it multiple times. Also I don’t believe they support instant status. ZigBee reporting tends to be faster (thus the Xiaomi).
I’ve also seen odd cases of local processing being slower than cloud processing so delay is not a reliable indicator of cloud vs local processing.