endian and proxy representation

[mop65715]

Given:
A [0..4] - where 0..4 represents a bit proxy 4 wide
B [5..8] - where 5..8 represents a bit proxy 4 wide
C [9..12] - where 9..12 represents a bit proxy 4 wide
D [13..16] - where 13..16 represents a bit proxy 4 wide

Lets assume MSB is defined as bit 0 on a Server implemention. Server transmits: 0xABCD
Client is little endian and receives. 0xCDAB. To account for endianness Client converts data to: 0xABCD. If the Client wanted to check a proxy (say 0..4 for the value 'A') the client must subtract 16. True/False? My counterpart made a comment about Server data being backwards and I'm not following his logic. In my view this is mandatory when you're dealing with endianess and nibbles.