I am not familiar with the module but in the docs it says:

Spaces, symbols and non-printable characters are only considered for splitting the string into its parts but not for sorting. For instance foo-bar-42 is broken in three substrings foo, bar and 42 and after that the dashes are ignored.

For the examples you give the sort order would then be:
 

P	007	B	YUM
P	007	YUM

 

P	007	Yum
P	007	b	Yum

 

P	007	b	yum
P	007	yum

 
Which to my mind is correct. You might be able to use some variation of the Schwartzian Transform to achieve your desired output.