If we assume AN-B/P to be of primarily restrictive then I agree, but at least by what I've seen in the manuals, theoretically the distinction is made due to the weight factor and there is a significant diagnostic crossover from AN-B/P to BN over time. You're right about there being several differences in practice though (at least in some cases, because I've also seen people on here who were diagnosed with AN-B/P and have said that their symptoms were pretty much identical to those of BN patients, as well as I have seen studies in which AN-B/P patients ended up exhibiting symptoms (both ED-wise and considering more general psychiatric pathology) more aligned with those of BN patients than patients diagnosed with AN-R, so the similarity cannot be entirely false either).
Perhaps maybe adopting a similar model to the one ICD-11 approached personality disorders with would be accurate? They stopped categorizing different personality disorders into seperate diagnosises and instead went for diagnosing just a personality disorder and then specifying the severity and most predominant traits/patterns.
Of course I'm not an authority of any kind, just a diagnostic manuals enjoyer and an avid research reader with some academic background regarding psychology and history of psychiatry who's not exactly fond of the idea of separating AN vs AAN, and AN-B/P vs BN based on weight alone, which to my knowledge seems to be the case both in theory, as per manuals, and in practice of at least some diagnosticians. That said, I'm nowhere near knowledgeable enough to give any definitive statements on such issues, so it was moreso just my (perhaps somewhat hopeful) intuition, additionally driven by the fact that ICD-11 in general tends to adopt more spectrum-like models , so it doesn't feel far-fetched to me that the next edition could take similar approach when classifying eating disorders, especially considering high diagnostic crossover rates between some of them.
EDIT: Btw, I believe I've seen a study that examined whether it would be reasonable to distinguish AN-B and AN-P from AN-B&P, and the results have shown that AN-B and AN-P are both in fact incredibly similar in their symptoms an general presentation to AN-B/P, and, if I remember correctly, resembled BN patients in certain (again, both ED-related and more general aspects) crucial areas too, thus differantiating all of them from AN-R patients regardless of whether they even binge eat at all.