Apple lossless (M4A) shows as 32 bit on 24 bit encoding

[Miss Sissy Princess]

The bottom line is that for ALAC encoded m4a files getting the actual bit depth would require using mediainfo which if there were a lot of these files in a collection would totally bog down the Library.

I had a couple more thoughts on this: 

1.  If MPD decided an album had 32 bit samples, just one call to mediainfo for one track in that album could confirm or refute that.  
2.  Actual recordings with 32 bit sample depth are really, really rare and will remain so.  If you had moOode assume that every "32 bit" track was really 24 bits, the display would be right almost every time, as opposed to being wrong almost every time.
3.  You're not the only one with this problem.  Here's an XLD trouble ticket talking about the same problem:  https://sourceforge.net/p/xld/tickets/433/

Note:  32 bit sample depth is probably a non-starter. There's not an audio DAC made that can do the 144 dB SNR required for 24 bits.  The best of them, which are balanced I/O, are in the mid 120dB range, which means that they might be good for 21 bits; even on these, the least significant three bits of a 24 bit sample are buried in the noise.  Now add in the SNR of the amplification, be it for speakers or headphones, and you lose more bits to noise.  Adding more bits doesn't improve anything.  It just wastes storage space, processing power, and money.