sort / Sorting order differs from gnusort (CR/FF)

While sorting large files I noticed a different order compared to gnusort. Took some time to create short test cases, here they are:

# ./coreutils --version
coreutils 0.10.0 (multi-call binary)

# gnusort --version
sort (GNU coreutils) 9.7
Packaged by Ubuntu (9.7-3ubuntu2)

Sort by key:

# printf 'aa\n0aa\r\n' | gnusort -k2,3 
0aa
aa
# printf 'aa\n0aa\r\n' | ./coreutils sort -k2,3 
aa
0aa

Dictionary order:

# printf 'a\rb\naab\n' | gnusort -d
aab
b
# printf 'a\rb\naab\n' | coreutils sort -d
b
aab

Same with numerical sort:

# printf '\r4\na\n' | gnusort -n
4
a
# printf '\r4\na\n' | coreutils sort -n
a
4

I suspect CR and FF treated as blanks?

Start by reproducing the three reported cases with the coreutils sort command and compare each result with GNU sort. Investigate how sort handles carriage returns and form feeds during key, dictionary, and numerical comparisons. Done means the listed inputs produce the same ordering as GNU sort.