yes, the entire flash area. which it will do when there is no other instruction to limit how many bytes to transfer.
did you miss the apparent file size problem i reported?
$ ls -l *dfu
131381 Aug 20 11:39 'Antenna Analyzer - 2 track 900 MHz default - nanoVNA_900_aa_20190802.dfu'
131072 Aug 27 17:12 nanovna_salamander_as_shipped_2Trace900MHz.dfu
16 Aug 27 17:11 nanovna_salamander_as_shipped_2Trace900MHz-option_bytes.dfu
131381 > 131072 .. of the firmware files available from the network drive, only that one is larger than 100000 bytes.
kb3cs