modifying block size to 512b is not working -> Defaulting to 4096b

xfs

I am trying to experiment with tracks and blocks. I was searching for a filesystem that still supports 512b as block size
and came across xfs.

I tried to chose the block size as 512b but it is defaulting to 4096 everytime.
I know that many filesystem (or may be all) adjust the block size based on the size of partition but could not get much
information that what is the partition when such transitions happen.

Partition size assigned with 'fdisk' : 200M

<pre>meta-data=/dev/sdb               isize=256    agcount=4, agsize=15630336 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0, sparse=0, rmapbt=0
         =                       reflink=0
data     =                       bsize=512    blocks=62521344, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=512    blocks=30528, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0</pre>


'sudo mkfs -t xfs -f -m crc=0 -b size=512 /dev/sdb'

And below block size verification gives:
sudo blockdev --getbsz /dev/sdb
4096

I am performing this for experimental purpose to learn more about tracks and sectors and corresponding filesystem.
Please let me know if I am doing something wrong.