It's possible, I've found the error:
  rdev->sb_start = sb_start;
is missing within md.c within /* minor version 0; superblock after data */
From my understanding, this means the new calculated superblock position isn't 
used.

I changed:

--- a/drivers/md/md.c    2021-09-30 08:11:08.000000000 +0000
+++ b/drivers/md/md.c     2021-11-11 14:54:10.535633028 +0000

@@ -2252,6 +2252,7 @@
 
                if (!num_sectors || num_sectors > max_sectors)
                        num_sectors = max_sectors;
+               rdev->sb_start = sb_start;
        }
        sb = page_address(rdev->sb_page);
        sb->data_size = cpu_to_le64(num_sectors);

I tested it with 5.10.46 and resizing with superblock version 1.0 is now 
working for me.

If this is correct, how can I get this into longterm 5.10.x and the current 
kernel upstream?

Many thanks in advance.


-- 
Mfg

Markus Hochholdinger