::I agree: There is no MBR on an unpartitioned PC medium such as a floppy disk, only a VBR.  The view that a floppy has both and they are one and the same is interesting but unconventional; I have been hacking on IBM compatibles since the XT era, before hard disks were standard equipment—and before I knew I was hacking—and this is the first I've heard that perception.  Historically, it goes against the fact that the MBR was invented as a surrogate VBR to get multiple volumes of the exact format that was conventional on unpartitioned media onto a single fixed disk (which was too large, at 20+ MB, to conveniently contain just one volume of the typical FAT16 [32 MB-limited, MS-DOS 2.0–3.2 ] type).  Since in the beginning there was no MBR, it is unhistorical to say the floppy disk's VBR was also an MBR.  However, that said, viewing things from a different perspective, "out of the box", can lead to useful insights that can ultimately lead to creative and sometimes even exciting new engineering ideas and solutions, so I want to express my respect for the thought and don't want to discourage unconventional thinking.  Despite its possible intellectual value, I just want to affirm that this particular description of the relationship between MBRs, VBRs, and floopy disks is not encyclopedic. 
 ::I also note that the distinction between MBR and VBR is at an abstract  software level above the BIOS.  I have just tonight added a clear exposition of this to the article, in the Programing Considerations section.  To BIOS, there are no MBRs or VBRs, only generic boot records which it loads, checks, and runs, giving them full control.  Based on this point, as for the ability of the MBR to function as a VBR conventionally does as well, I think it's absolutely possible.  The assertion that an MBR or VBR directly loaded by the BIOS boot loader can do anything clearly implies this.  The only special technique needed would be for the boot record, when behaving as an MBR, to pass some signal to the VBR which it itself could use to detect that it was being called as a VBR (i.e. by an MBR) and not as an MBR, or for it when acting as an MBR to detect when the VBR was itself and to then jump to its VBR entry offset (not at 0) instead of its MBR entry address (at 0).  Doing either of these is trivial and many methods are obvious.  (Therefore, there is no need for it to be explained in the article, even if it were established published work).