I think a lot of tapers are mislabeling and minimalizing the wave recorders with a digital input as being only a "bit bucket". When a DAT recorder was patched out of an outboard A/D, and it captured the linear digital audio stream, that truely was nothing more than a "bit bucket".
A wave recorder is a small computer. Regardless of the memory storage used, HDD or flash memory, what these recorders are doing exceeds what a DAT recorder did.
The recorder is taking either an analog input run through it's own A/D, or a PCM digital audio stream through it's digital input, and writing the information to a workable computer file type, wav, bwf, aiff, etc.
The idea of a recorder that does all this, and then uses an outboard file storage medium is not hard to imagine. I could think of a recorder where a USB drive can be popped into the side, for example.
However, when I think of most flash recorders, their size is dictated by the inputs and control surfaces, not the memory system. A recorder offering full size XLR connections, for example, would not be any smaller if the flash card slot was left out.