My test shows no overscan using PS3 player with Matrix DVD (in RGB mode):
The overscan occurs when the PS3 player video output format is set to Y Pb/Cb Pr/Cr or Auto (even with 1:1 mode).
Looks like the original 300 image from the test here was taken with the default settings (which actually uses Y Pb/Cb Pr/Cr format).
I'm not sure why such problem happens with Y Pb/Cb Pr/Cr, but not with RGB. Can it be PS3 issue or generic format limitation, or is it specific to Dell?