Software flow offloading implications

It's working if the SQM interface set as wan (device), but software flow offloading does not help with SQM if the interface set as pppoe-wan (tunnel). My test on my friend's FTTH line with 200/20 plan showed that Xiaomi Mi Router 4A Gigabit Edition is able to shape up to 150mbps using CAKE without software flow offloading and it's fine doing 200mbps with software flow offloading turned on. But I'm afraid Diffserv is not working when shaping is done on wan instead of pppoe-wan, every packet goes into Best Effort tin. Othen than that I wasn't able to test if nat option is working, so not sure about that.