These are minhagim, that is nedarim taken by our fathers and grandfathers. So, RebE’s grandfathers took on different observances than someone else’s. No need to argue…
What about Sephardim, who exchanged wine in av for selichot in elul. As this year a week before tisha bAv is same as rosh hodesh, do you have shorter selichot? Or you still need to atone for rice on pesach?