Are you seriously claiming that a single 7713 with 64 cores can outperform dual 7742 with twice as many cores? Are you certain it wasn't a dual socket system? The processor will support two sockets (it's not a single socket P version). The 7742 is also a 64 core processor. It's the best AMD has to offer in the Rome generation except for the 7H12 which is intended, I believe, for supercomputers. That would mean about double the IPC. Surely, that sounds suspicious. Or do you not think about what you write? 8280L has 28 cores so it's not surprising it plays the same league (4x28 = 112). Although, you've got to be desperate to buy Platinum Xeons. They're not good value at all. Aimed at banks or oil companies.
Assuming the stated frequency is base, I wouldn't bet on it getting much, if at all, higher. In servers, efficiency and power density matter a lot. You can have over a hundred processors in a single rack. At 200 W per socket, you're talking 20+ kW. From a single rack. And from processors alone. The higher power processors tend to be intended for specialized applications which might employ liquid cooling to deal with the density.