I think you've got it all down
On NVFS devices, the cache gets cleared whenever a program requests more cache space than is currently available in a contiguous block -- this is what causes those long Blazer load times. Unfortunately, any time a program requests a chunk of DBCache as Protected, that chunk can't be flushed without a reset -- this eventually results in severely fragmented DBCache, with lots of free cache, but all in unusable tiny chunks.
However, one of the other upsides to UnCache is that it decreases the time it takes to reset a Palm; I generally reset mine now before using any memory intensive app -- takes about 12 seconds; less time than it takes to flush the DBCache when launching Blazer.