Mopidy plays sound with 24bit although file is in 16bit resolution

First off, I’m using Mopidy 2.0.0 on Raspbian.

My sound config looks like this:
mixer = alsamixer
output = alsasink device=hw:1,0

card = 1
control = PCM

enabled = false

If I play a 16bit/44.1kHz mp3 file, the command “cat /proc/asound/card1/pcm0p/sub0/hw_params” produces the output:
format: S24_3LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 441
buffer_size: 8820

I also tried this:
gst-launch-1.0 playbin uri=file:///xxx.mp3 audio-sink=“alsasink device=hw:1,0”

and get the same output when analyzing the used resolution.

Why is the data converted? Shouldn’t it play with 16 bit resolution?

p.s.: If I change part of the gst-launch command to audio-sink=“level ! alsasink device=hw:1,0” the file is played with 16 bit.