About why PSP-1007 can't use software Downgrader :P

i buy a PSP-1007(Taiwan Ver) to find why this model can't use software Downgrader :P
i check the Hardware inside PSP-1007, it is same as other PSP

i use Hardware Downgrader make it to FW1.00
and try use FW1.50 EBOOT.PBP to update it but not success
the error same as software Downgrader :P

and then i use my FW1.00/1.50 Up/Downgrader program update it to FW1.50
that work :)

so PSP-1007 can't use software Downgrader, the problem is not on the PSP-1007 Hardware
the problem is it can't run FW1.50 update EBOOT.PBP :P