IIRC, iOS does not have an equivalent to the Virtualization.framework found on Apple M1 machines, which means CPU virtualization instructions do not exist or are not accessible from userspace.
From what I can see from the code, UTM uses "JIT based acceleration using qemu TCG". With a quick Google search I found that TCG "is the core binary translation engine that is responsible for QEMU ability to emulate foreign processors on any given supported host."