For WebMAN Mod they are valid
@sandungas.

At least in theory (I'll test it today if it's possible from play it from internal HDD).
@aldostools integrated those changes:
http://forum.redump.org/topic/14472/ps3netsrv-modified-for-encrypted-3k3yredump-isos/ with WMM.
Years ago games cannot be launched from disc images but unpacked on HDD to imitate digital category because that was the only known way in those times (times which dongle payloads started). But now we have Cobra, and we can mount images like real discs. I don't see a reason to using decrypted hand made *.iso instead to proper one.

The only flaws as I mentioned are wasting 256MiB space for each game as consequences of *.pup on every disc and lack of modding capabilities which doesn't matter in archiving purpose. And the most important benefit here, they can be dumped on PC a lot faster than on PS3.
About efficient: I highly doubt as not whole disc is encrypted, just part of it, and decryption is doing on the fly.