I'm sorry, I have never fully understood most of the posts you write. When I look at the manufacturers specs and Q&A the drives site they state that this drive cannot be used to it's full extent under XP or other OS as an MBR drive because the advanced formatting to make 4K sectors is no longer supported. So it exposes itself as a regular disk with 512 byte sectors and must be GPT to use the full 4TB capacity. If you mean something else by your statements I am afraid they are above me and I can't figure out what you are meaning.
This WILL work with BIOS / MBR boot, but only if I set it to MBR disk type type and then create partitions that equal less than 2TB in size. The remaining 2TB just sits there as a dead thing totally inaccessible. I did this to one of them in order to have another Easy2Boot bootable drive. The other 2 I just set to GPT and formatted without any boot method for them.
The whole point, or if you prefer the "novelty" of the (allow me "clever") approach I devised and proposed here:
is that there has been a lot of confusion (cannot say whether intentionally or by mistake) by the good MS guys (and by the various hard disk manufacturers) abut the exact nature of the 2 TB limit.
What has been written all over is that a disk bigger than 2TB cannot be accessed if MBR style.
This is FALSE.
The origin of the issue is that 2 fields in the MBR partition table entries, the "Sectors Before" and the "Number of Sectors" are 32 bit, and as such the biggest number you can store in that is 2^32-1, i.e. 4294967295 which, mutliplied by 512 makes 2199023255040 bytes, which is the advertised 2 TB "limit".
Actually you can have a first partition ending just short of sector 4294967295, and another partition following it with a size sightly less than 4294967295 sectors.
This way all the sizes "fit" in the respective fields.
Then - for *some* reasons - the XP disk drivers cannot access the second partition, BUT the Windows 7 ones (since they can access just fine the same extents when the disk is GPT) have no problems whatsoever with them.
So, out of a 4 TB disk (while still MBR style) you can fit:
1) a first partition almost 2 TB in size that will be accessible by *any* OS <- or up to 3 primary partitions as long as they are all contained in the first 2 TB
2) a last partition, up to almost 2 TB in size that will be accessible only by Windows 7 and later
you can find an image where you can see a Windows 7 with this setup, with a first partition of almost 2 TB and a second partition of roughly 600 GB on a 3 TB disk.
If you read the thread from the link I gave before up to the above, you will understand how the good MS guys do not support this partitioning scheme in diskpart or disk manager, so the partitioning needs to be done manually (but it is doable).
Of course it is "experimental", it is potentially "dangerous", etc., etc., but neatly offers you a way out to fully use the whole 4 TB disk while keeping it MBR and BIOS bootable.
The alternative (already given) is to have it GPT but make it anyway grub4dos bootable, though obviously "normal" automated tools like East2boot won't work with this latter scheme.
 not fully tested, it may depend by the specific hardware/disk controller