It looks like the confusion about radiator compatibility can be solved by simply saying that the current revisions of the cases are compatible with all
Asetek branded AIOs. Looking at CoolIT's
website, the OEM for the Corsair H115i RGB Platinum, it looks like ALL of their radiators in the "High Performance" SP family have squared off ends. Corsair uses these radiators for their Corsair One prebuilt, and those also have the squared off ends. As more manufacturers look to move away from the Asetek dominated AIO market, we may end up seeing more of these CoolIT radiators rebranded and sold on the market.
At this point, with only a single radiator being incompatible with their case, I think it's important to remember that no one is perfect, even companies, and
@KSliger has been incredibly transparent with informing everyone about issues as they have arisen. There is a point at which customer entitlement ends, and common sense needs to take priority. The hardware swap subreddits are an option for reselling or trading for compatible coolers, along with local digital marketplaces such as Facebook Marketplace, Craigslist, etc. Gamer Nexus'
review of the H115i Platinum AIO shows that performance compared to the Asetek 280mm AIOs is nearly identical. If you are invested in the Corsair ecosystem and are not willing to sacrifice or change those parts, then your option is asking for a refund or waiting for Sliger to push out the revision...which if the SM560 is any example, probably will not take long at all.