While the Phantom Ruby is seen in both the Modern and Classic Universes, it's clear that what the ruby is capable of differs between the two. Most notable of this is the literal warping of space and time which transports Classic Sonic into the Modern dimension. Had this all been nothing but virtual reality perception BS, then Classic Sonic wouldn't end up in the REAL modern dimension but in an illusionary one. Now, consider this: What if there are TWO phantom rubies? One in the Classic dimension which is that legendary eighth timestone (or rather a Master timestone) and one in the Modern Dimension that creates illusions? Given the events of Sonic Forces (including the prequel comic) may just be about a year of events, it doesn't line up too well with Sonic Mania. Keep in mind that the Ruby in Mania was indeed the original in that it was usable by multiple parties (Robotnik, the Heavies, and possibly Classic Sonic at the end). So unless for some unnecessary reason that at the end of Sonic Mania, the phantom ruby is sent back in time in the Modern Era (or Classic Sonic sent forward), it seems to me that both the modern Eggman and Classic Robotnik had an original phantom Ruby at the same time. Now, the one chink in this is that at the end of Sonic Forces, Classic Sonic doesn't go back until the Phantom Ruby is destroyed (I don't know if this is ever stated anywhere but it is what happens). Granted, it took what looks like several hours for that to happen but whatever.