That is surprising. I was considering buying the 215 and 225 Sierra and using whichever shot best. I've had good luck with Sierras running them in 26-2800 ft/sec velocity range. I shot a couple deer last year with the 180 Sierra Prohunter from my 308. Recovered 1 bullet - 141 gr/78% retention after penetrating about 2 feet of deer (head-on shot). I could like that same result in a 338-06 on elk.
There is a fellow over on Nosler that uses the 225 Sierra in a 338 RUM and has nothing but praise for it on elk. I have used the 225 Sierra to do initial load work up for the 225 Partition and it seemed to shoot great, never have taken an animal with one though. I have heard all of the same things about the 215 Sierra being pretty hard so I have always wanted to try it out of my 338 Win just to see what it did in jugs as well as at distance, but I haven't had the time to do it just yet. I can't see a soft point bullet like that not expanding decently at 2600.. Seems crazy. Wonder if Sierra got the cores monkeyed up in a production run, cause typically I haven't ever seen any really hard Sierra's out of much of anything, good bullets, just not exactly hard..
