file system recognition on Windows and BIOS parameter block position

Question

I am writing a boot sector for the FAT12 file system for a floppy disk.

Code #1:

start: jmp main
TIMES 3 - ($-$$) DB 0
OEMname: DB '12345678'
;rest of the BPB information below

Code #2:

TIMES 3 - ($-$$) DB 0
OEMname: DB '12345678'
;rest of the BPB information below

In both these cases, OEMname starts from byte 3 (as informed by the assembler listing).

When the boot sector is written to the disk, Windows recognizes the partition when code #1 is used but fails to recognize when code #2 is used, i.e. it complains that the drive is not formatted.

Why does Windows succeed to identify the file system in one case but not the other?