Latitude e5570 BIOS Password Prompt Screen On External Monitor

Our firm has had many Latitude e5520, 30, 40 and 50 computers over the past 6 years.  I always set up the BIOS system password option.  We also use the Dell port replicators with multiple external monitors.  When the user turns on the computer using the power button on the port replicator the BIOS password prompt screen would appear on the external monitor so they can enter the password.  We have recently purchased 5 new Latitude e5570 computers.  I set up the BIOS password on these new computers just like I have done in the past on the older models.  However it seems that the Dell logo and the BIOS password prompt does not appear on an external monitor.  I removed the computer from the port replicator and connected a VGA monitor to the external monitor port on the back of the e5570 and still the BIOS password screen does not appear.  I have to open the laptop to view the BIOS password prompt to enter the password then the external monitor will display the Windows 7 boot up screen.  I spoke with Dell tech support and they said that this is normal.  How can this be normal when all Latitude model e5520, 5530, 5540 and 5550 never had this problem. I even downloaded the most recent BIOS update and that did not fix the issue.   I cannot have the user open the laptop just to see the BIOS password prompt.  I told Dell support that something is not right with their BIOS software but they again said the e5570 is working as designed.  I just can't believe it.  Anyone have any suggestions on how I can get the BIOS password prompt to appear on an external monitor?

Thanks,

Charlie