You may view this as a disadvantage of binary. Of course the information defining this start could be defined differently. There is NO restriction of one value to each keyword. David suggested that we don't use loops e.g. for the size of various dimensions, so that the one available level of looping is available for other, presently undetermined, purposes. The CBF document is presently written on this basis.
Some vision is needed here.
The view of the imageNCIF group has tended to be that efficiency and simplicity are the main priorities. Restrictions of block boundaries, and even word boundaries could all be removed, BUT with the price of less efficient access, and extra complication in the code. This would add extra functionally which is not obviously desirable. YOU would still have to strip it off. May be we should start the discussion again without this restriction.