I also thought it was a bit faster than I normally do my long runs, but I was just keeping up with you.
I think your distance is a bit underdone - the map you sent showed the distance of the loop as 29.6, which means probably close to an even 30 once you factor in the detour at Royal Park, hooking under a couple of bridges etc. I also got the distance to/from as 2.8, although that includes the bit to/from the pipe bridge.
OK, I'm happy to go with your calculations.