It depends on maskset revision of MCU which is assembled on your TWR-K60N512 board.
According AN4533:
Kinetis 100 MHz revision 1.4 or later required. The mask set number marked on the
package is 4N30D. Subsequent revisions may be marked 5N30D, and so on. Revisions
earlier than revision 1.4, may not support swap or may disable the Erase-All-Blocks
command after swap initialized. Thus, on those early revisions, some debuggers will not
be able to re-download to flash if they rely on the Erase-All-Blocks command to preerase
the flash. Additionally, it was not possible to set the swap system back to
uninitialized on those early devices.
So, Flash swap as is described in this AN and as it works in flashX driver will not work with old masksets 0M33Z, 0N30D, 1N30D and 2N30D.
Since some of TWR-K60N512 was assembled with oldest maskset 0M33Z and some of them was assembled with 4N30D, MQX doesn't contain directly project for TWR-K60N512 board.
I hope it helps you.