du -BM behaves differently from GNU version

du -BM does not print unit:

sveta@lemurr:~/src/thirdparty/coreutils$ du --version
du (uutils coreutils) 0.8.0
sveta@lemurr:~/src/thirdparty/coreutils$ du -BM | head
2	./man
1	./.git/refs/heads
1	./.git/refs/tags
1	./.git/refs/remotes/origin
1	./.git/refs/remotes
1	./.git/refs
1	./.git/objects/info
51	./.git/objects/pack
51	./.git/objects
1	./.git/logs/refs/heads

Here is the output of the GNU version:

sveta@lemurr:~/src/thirdparty/coreutils$ ./src/du --version
du (GNU coreutils) 9.11.131-68f15
Copyright (C) 2026 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Torbjörn Granlund, David MacKenzie, Paul Eggert,
and Jim Meyering.
sveta@lemurr:~/src/thirdparty/coreutils$ ./src/du -BM | head
2M	./man
1M	./.git/refs/heads
1M	./.git/refs/tags
1M	./.git/refs/remotes/origin
1M	./.git/refs/remotes
1M	./.git/refs
1M	./.git/objects/info
51M	./.git/objects/pack
51M	./.git/objects
1M	./.git/logs/refs/heads

Start at the du command entry point and reproduce the shown du -BM output alongside the GNU example. Trace the handling of the -BM option and verify that completed output includes the M suffix without changing other units or paths.