Is it possible to change volume with no reencode with ffmpeg?

I just had this question because I used the following command with ffmpeg:

ffmpeg -i input.wav -filter:a "volume=0.2" output.wav

Following the documentation here: https://trac.ffmpeg.org/wiki/AudioVolume

However, when I created the new file, the output was half the size of the input and the bitrate of the audio track was reduced as well.

So my questions are:

1. Is the bitrate supposed to decrease with decreasing and increasing volume like so?
2. Is it possible to change volume without reencoding with ffmpeg?

Okay as someone from Reddit kindly explained to me, I should be able to change the volume without reencoding, however, my input codec was pcm_f32le and the default setting for the output codec for ffmpeg without any specifiers is pcm_f16le.

The first one pcm_f32le is 32 bits, so it stores more information than the second which is 16 bits.

So the answer is:

1. Yes it is because in this case I was reencoding unknowingly to a codec with less information.

2. Actually no, it still reencoding. The best option is to use the same code I used above with an extra specifier:

ffmpeg -i input.wav -filter:a "volume=0.2" -c:a pcm_f32le output.wav

The codec for input and output must be the same as in both 32 bit or 16 bit or else I have to add a specifier which I was shown how to do by the same person on Reddit.

However, this is still reencoding whenever you add a filter.