But it's not a performance issue, it's more to do with system duplication/redundancy and the sophistication of the stabilisation/autopilot.
I have flown single engined floppy stick helicopters i.e. no stick trim, let alone an autopilot, in IMC, quite legally, under military rules. I also used to fly a public transport AS355N (twin) with a "floppy stick", at night (normally in UK, by definition, under IFR as there is no VFR at night here).
There was a likelihood that sometimes we might go inadvertently IMC at night due to the nature of the job, and we were required to train for that eventuality. However, it's all been outlawed now after some high profile accidents at night.
Not before time. The FAA seem to be lagging behind, now to an alarming degree, it seems.