No this isn't just using the "test m33" option in DCv6. Well sort of is...
Time machine is required.
Install DCv6 onto you memory stick now take jas0nuk's resurrection.elf from the pandora elf menu tool he has released. I'm using v0.4 not sure if older versions work. Now go into your TM/DC6/kd folder you will see resurrection.prx, back this up then delete it from the folder now paste in the resurrection.elf rename the extension to .prx. Now go to the TM folder and open your config.txt file, ensure there is a line saying TM/DC6/ipl.bin and its bound to a key. Plug in your magic memory stick with dcv6 on and then put in the pandora battery while holding down the button the DC6/ipl.bin was bound to.
Et voila 4.01m33 should boot off the memory stick just like time machine firmwares and no need to go into DCv6.
Obviously you need to be on a different firmware to notice the difference. I've tested this on my 3.95gen-2 phat 5 times and its worked. Perhaps it only works on phats can others test this? My slim is already on 4.01m33.