Why 'df' does not honour '-t' argument ?

Issue

• df does not honour -t argument
• df when used with -t stats all types of filesystems

[root@hostname ~]# strace -e stat df -Tht xfs
stat("/", {st_mode=S_IFDIR|0555, st_size=254, ...}) = 0
stat("/sys", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
stat("/proc", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
stat("/dev", {st_mode=S_IFDIR|0755, st_size=3320, ...}) = 0
stat("/sys/kernel/security", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
stat("/dev/shm", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=40, ...}) = 0
stat("/dev/pts", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
stat("/run", {st_mode=S_IFDIR|0755, st_size=1280, ...}) = 0
[..]
Filesystem                              Type  Size  Used Avail Use% Mounted on
/dev/mapper/vg00-lv00                   xfs   4.1G  3.1G  1.1G  74% /
/dev/vda1                               xfs  1014M  161M  854M  16% /boot
/dev/mapper/vg00-lv01                   xfs   2.0G   39M  2.0G   2% /home
/dev/mapper/vg00-lv02                   xfs   1.9G  1.7G  293M  85% /var
+++ exited with 0 +++