One possible way to distinguish between both would be continuity: if you had a Bitcoin node running several months before the announcement, and kept running the

One possible way to distinguish between both would be continuity: if you had a Bitcoin node running several months before the announcement, and kept running the same unchanged software until today, which one would your node be following now? That one probably has a bigger claim to both being the "real" Bitcoin, and having the plain unadorned "Bitcoin" name. As to whether it merits having "Bitcoin" in the name, both are close enough that one could be considered a small variant of the other. That might be enough for the other one to merit being called "Bitcoin something".