Memory contains all sorts of potential evidence, from encryption keys to malware to passwords. Failing to collect this information can significantly hamper or even kill an investigation.
The research into freezing and then extracting RAM contents was interesting, but not terribly practical.
Flash is the unusual case since it needs to be "flashed" in bulk before it can be rewritten.
Many media have special requirements for writing. It's true that DRAM and SRAM don't have a separate "erased" state, and neither do fuse PROM, core memory, Williams tubes, acoustic delay lines, or magnetic disk and tape.
But CD-R, Flash, CD-RW, rewritable magneto-optical disks, two-photon storage, and some other memory types have a distinct "erased" state; in some cases, you can't even return to that state. I'm not sure about MRAM, FeRAM, PRAM, and hypothetical memristive memories.
Whether this erase procedure happens immediately upon the user's request to delete the information or whether it's added to a queue of areas to erase (the "purging routines" or "garbage collection" mentioned in the article) is a small detail. A modern OS will return control to the user immediately upon issuing the command, and all that matters to the end user is that the erase command is issued before the next write. A firmware
I seriously hope that these researchers aren't advocating a mandate that states that the erase procedure cannot be issued until a write is requested to that space.
In any case, I still think your point is valid despite disagreeing with you, and I think it's disappointing that you just received a downmod. I've just upvoted you back to 1.
In NAND flash, overwriting isn't even an option, although I don't understand why.
SSDs are completely different. The optimisation no longer works, since flash memory has no overwrite operation, only a block-erase operation (which is a slow operation - and the erase blocks are relatively huge). In order to stay efficient, SSDs must perform background free space management, which includes erasing unused blocks in advance in order to be ready for new data.
This should be obvious to anyone who understands how flash memory works. SSD manufacturers have no option here. It's a fundamental side-effect of the technology.
"Forensic analysis" that depends on an optimisation performed on a system using a hard drive will no longer work with a different technology that cannot use that optimisation. They were exploiting something that is not necessarily going to be possible any more.
If they want a clean equivalent of a "write blocker", they are going to have to somehow disable the SSD's background management before powering up the drive. This might not help so much though if the background management has already erased unused blocks after the user deleted files.
I will accept though that this means that people working in the field will need to change their procedures.
Summary: forensic analysis only works because of an optimisation that systems using magnetic hard drives did but systems using SSDs can't. How is this surprising?