In general, cryogenic treatment is one of those things that falls into the "it won't hurt" category. Amongst barrelmakers, Krieger is an advocate, others are not.
Cryogenic treatment will not relieve stress in a barrel blank as will conventional stress relieving by heating. Those makers who cryo treat their barrels also stress relieve prior to the cryo.
If there is any real improvement imparted by the cryogenic treatment, it is probably an improvement in surface finish and machinability. I doubt that it is cure for a poor shooting barrel but it won't hurt a good one and may make it last longer.
In the end, cryogenic treatment is really unproven. If a barrel is not stress free, cryo is unlikely to make it so. If it is stress free (and most good custom barrels are) cryo MIGHT add to barrel life by improving interior bore finish and durability. Will it double barrel life? No, it will not. Will it cut groups in half? No, it will not. Will it do any harm? Again, no, it will not. GD