I don't think they'd admit much about it even if they had one internally, both because Apple isn't known for their openness about many things, and because they already exited the dedicated server hardware business years ago, so I think they're likely averse to re-entering it without very strong evidence that it would be beneficial for more than a brief period.
In particular, while I'd enjoy such a device, Apple's whole thing is their whole-system integration and charging a premium because of it, and I'm not sure the markets that want to sell people access to Apple CPUs will pay a premium for a 1U over shoving multiple Mac Minis in the same 1U footprint, especially if they've already been doing that for years at this point...
...I might also speculate that if they did this, they'd have a serious problem, because if they're buying exclusive access to all TSMC's newest fab for extended intervals to meet demand on their existing products, they'd have issues finding sources to meet a potentially substantial demand in people wanting their machines for dense compute. (They could always opt to lag the server platforms behind on a previous fab that's not as competed with, of course, but that feels like self-sabotage if they're already competing with people shoving Mac Minis in a rack, and now the Mac Minis get to be a generation ahead, too?)
I will add that consumer macOS is a piss-poor server OS.
At one point, for many years, it would just sometimes fail to `exec()` a process. This would manifest as a random failure on our build farm about once/twice a month. (This would manifest as "/bin/sh: fail to exec binary file" because the error type from the kernel would have the libc fall back to trying to run the binary as a script, as normal for a Unix, but it isn't a script)
This is likely stemming from their exiting the server business years ago, and focusing on consumer appeal more than robustness (see various terrible releases, security- and stability-wise).
(I'll grant that macOS has many features that would make it a great server OS, but it's just not polished enough in that direction)
As I recall, Apple advertised macOS as a Unix without such certification, got sued, and then scrambled to implement the required features to get certification as a result. Here's the story as told by the lead engineer of the project:
This comes up rather often, and on the last significant post about it I saw on HN someone pointed out that the certification is kind of meaningless[1]. macOS poll(2) is not Unix-compliant, hasn't been since forever, yet every new version of macOS gets certified regardless.
I wouldn't run a Windows server, but at least it can manage a SYN flood, whereas MacOS doesn't have syncookies or similar (their version of pf has the syncookie keyword, but it seems like it only works for traffic that transits the host, not for traffic that is terminated by the host). Windows also has some pretty nice stuff for servers like receive side scaling (afaik, Microsoft brought that to market, or at least was very early).
In particular, while I'd enjoy such a device, Apple's whole thing is their whole-system integration and charging a premium because of it, and I'm not sure the markets that want to sell people access to Apple CPUs will pay a premium for a 1U over shoving multiple Mac Minis in the same 1U footprint, especially if they've already been doing that for years at this point...
...I might also speculate that if they did this, they'd have a serious problem, because if they're buying exclusive access to all TSMC's newest fab for extended intervals to meet demand on their existing products, they'd have issues finding sources to meet a potentially substantial demand in people wanting their machines for dense compute. (They could always opt to lag the server platforms behind on a previous fab that's not as competed with, of course, but that feels like self-sabotage if they're already competing with people shoving Mac Minis in a rack, and now the Mac Minis get to be a generation ahead, too?)