Doubt of what?
LIST is a directive; a directive it is a command or information for the assembler or linker to make it behave in a certain way. It is not part of the program but can control how the program is compiled.
In the MPLAB IDE, as in other IDEs, you set the processor type in the IDE project setup. So, everything knows what processor you are writing code for.
In that case, LIST p= is not needed. It does no harm (provided it matches the processor set in the IDE project) but it is superfluous.
If, however, the assembly code is to be compiled by a command-line compiler, possibly separate assembler and linker, then you need to tell them what processor they should compile the assembly code for. The best way then is to use the LIST p= line.