It's likely because it won't really be a toubunkiller more than it'll be something that helps the earlier brand more. The former will kill itself before the latter does anyway
Negi literally said 5toubun will end in less than a year, that's why we're getting mach 10 pacing all killer no filler which is bad, i need more quint SoLs
If anything, if this thing manages to become the non-serious family drama not-too-much-plot version of 5toubun it'll get the initial toubun readers who's interested in more harem shenanigans. Not to mention the drought of proper romcom harem these days.