My view of the importance of cursive writing symbols of any language, be it hieratic, Arabic, English, or any modern language, is that artists and language people chose them. There is little of significance that math historians can deduce from a hieratic number 'symbol' data base, so I do not consider the issue.
What I do consider is that I have never asked why any particular English cursive symbol was chosen. A close association with the printed 'letter' is all that is needed. Am I missing something?
In the case of hieratic number symbols, they were ciphered versions of the standard 'alphabet', no more, or no less. Of course, philologists do not consider hieratic 'letters' to be letters.
It may be important to note, for far too long, transliterations of hieratic to hieroglyphic shapes and traditional meanings were used to discuss hieratic meanings. Little of general importance that can be gained from this approach. Each hieratic texts must be read in context, compared to like texts to fairly deduce the meaning of each hieratic symbol.
That is, the artistic imagery that scribes first used to create hieratic symbols will always be open to question. Philologists discuss this issue in ways that likely have very little to do with the ciphered image of a particular hieratic number symbol.
For example, the healed 1/64 hekat, denoted in hieroglyphic, is less clear in its ciphered hieratic form. The healed nature of the dja hieratic symbol was only reported in 2002,and validated in 2005. The dja and 1/64 symbols Akhmim Wooden Tablet and RMP applications are still being debated.