DIR-882 and HW offload


I used yesterday's https://downloads.openwrt.org/snapshots/targets/ramips/mt7621/ to flash OpenWrt for the first time on this router.
Initially even LUCI was not installed, I had only SSH. Installed luci, uhttpd and then started testing the NAT speeds. By default, 250/500mbit (no offloading). I enabled SW offload, raised to 380/500mbit. Checked HW offload also as I have the MT7621, doesn't make a difference, same 380/500mbit. Speedtesting directly my connection, I get ~800/500mbit so clearly on the download side, OpenWrt is limiting and HW offload doesn't seem to make a difference.

Is MT7621 HW offload broken or should I do some additional configuration somewhere?