Why does Dell still refer to the UEFI as the BIOS?

Dell, in general, has over 150,000 employees.  The core engineering and technical groups do use proper technical terms to differentiate between legacy BIOS and modern UEFI firmware.  An example of the difference was explained here https://www.youtube.com/watch?v=VY3flvge2X0.  The remaining groups, from warranty supports to technical writers, are working at their skill levels.  While some did not know the differences (many errors with technical info during copy and paste when updating users manuals are examples), others were just working along with the system and didn't bother with anything outside of their scopes.  Dell is too big for any centralized group to bring everyone on the same page.

But, I think the main focus point is customers.  While providing tutorials and knowledge base to customers with new and modern technology information, Dell still keep support site with the same or similar terminology, making it easy to comprehend and follow.  Although, many are still struggled to understand.

Whichever the language can be understood during communication is more important than playing the grammar police.  Either BIOS or UEFI, they are located at the same place (on motherboard), instructions for accessing, edit settings are the same.  To most computer users, they are practically the same thing, UEFI is just a newer and better BIOS.