My understanding (which may be mistaken) is that modern MLC and TLC SSD cells for all intents and purposes are binary; while they may have some small analog charge-holding ability, the controller compensates for this, and you can't separate the chips from the controller and try to read them in an analog fashion (because the block map is held by the controller, so once the chips are parted from the controller their contents might as well be random).
And some SSDs have a function called "DZAT," or "Deterministic Zeroes After TRIM"--basically, the controller always returns 0 for any page that's been cleared by TRIM and not rewritten. It doesn't even attempt to read the cells, so even if a ghost or residue of the old data are still in the pages, it doesn't matter. (The opposite, DRAT or Deterministic Read After TRIM, will have the controller attempt to read TRIMmed pages anyway, so if they haven't been physically reset by the controller's garbage collect you may still get some remnant of the old data.)
And, of course, zeroing the page resets that ghost anyway, so once the garbage collector has been by, again my understanding is even forensic software can't recover anything useful.
Of course, this assumes TRIM is implemented properly. Some SandForce SSD controllers are known for buggy TRIM, and these drives may indeed leave traces of information on "unused" blocks because the garbage collect doesn't properly sanitize TRIMmed pages.
