Found the answer in a different post [1]. The hypervisor and virtual machines are single-core only. The talk also indicates that all I/O operations need to be manually rewritten to use the instrumented mechanism, so it demands a highly paravirtualized guest OS. Logically, that means there are probably no cross-VM shared memory interfaces either. So, no shared memory and thus no need to deal with shared memory non-determinism.
This is just a standard replay engine from what I can tell.
At timestamp 23:40 in the video by Alex Pshenichkin from 2024-06-10 it says data ingestion comes via VMCALL interactions. As such a call is literal nonsense if you are not virtualized, any such call inherently means you are using a paravirtualized interface. Now maybe FreeBSD has enough standardized paravirtualized drivers similar to virtio that you can just link it up, but that would still be paravirtualization solution with manual rewrites, just somebody else already did the manual rewrites. Has the fundamental design changed in the last 3 months?
This is exactly a replay engine (or I guess you could say replay engines are deterministic simulators). How do you think you replay a recording except with a deterministic execution system that injects the non-deterministic inputs at precise execution points? This is literally how all replay engines work. Furthermore, how do you think recordings work except by recording the inputs? That is literally how all recording systems designed to feed replay engines work. The only distinction is what constitutes non-determinism in a given context. At the whole hypervisor level, it is just I/O into the guest; at the process level, it is just system calls that write into the process; at the threading level, it is all writes into the process. These distinctions are somewhat interesting at a implementation level, but do not change the fundamental character of the solution which is that they are all a replay engine or deterministic simulator, whatever you want to call it.
This is just a standard replay engine from what I can tell.
[1] https://news.ycombinator.com/item?id=41501577