Way back we had threads about whether a load tester (as used for starting batteries) would be a valid test for deep cycle batteries. Some people said no, you had to do the 20 hr rate test to 50% at the 20 hr rate as I have described above.
Mex refers to a load test but wants a "real one" not the garage typical load tester they have.
I don't remember that this ever got resolved, but I am happy with the ten hour load test method, having done it several times and have confidence in it by subsequent results and lots of cross-checking.