You said that a safety pilot can log instrument time as well. Being in IMC would disqualify the need for a safety pilot.
That would make you wrong on two counts.
First, I said nothing about IMC, but we'll address it anyway. You made the assumption that I stipulated IMC, whereas I did not. The FAA has held that one need not be in instrument meteorological conditions in order to be in instrument conditions. The FAA has held that any circumstance requiring the use of intruments to maintain control of the aircraft, to include a moonless night over water or flight between cloud layers, constitutes instrument conditions. Further, the FAA has held that one who does not posses an instrument rating may log instrument time under such conditions...without ever being in IMC.
So far as the necessity of a safety pilot while in IMC...you're wrong there, too. So long as the pilot flying wears a view limiting device, is under a hood or a cockpit blackout device, or is otherwise prevented from seeing and avoiding other traffic, the safety pilot is required. The safety pilot's primary duty is seeing and avoiding other traffic (further reinforced by the subsequent requirements under 91.109 for additional observers where necessary to see traffic where the safety pilot's field of view may be obscured).
The requirement to see and avoid does not go away in IMC, nor in instrument conditions. As you have just learned, IMC and instrument conditions are not necessarily the same thing. A safety pilot is required so long as the flight engages in simulated instrument flight. That the flight may actually require instruments to maintain control does not negate the fact that one pilot may be wearing a view limiting device or otherwise constrained from the ability to see and avoid other traffic, or the fact that he or she has no choice due to artificial means of restricting his or her vision outside the cockpit, but to fly by reference to instruments.
The truth is, a pilot may be in instrument conditions and not in IMC, and a pilot may require a safety pilot while flight in instrument conditions or IMC.
What you described was a single pilot operation...
I described no such thing. Perhaps you're not so bright. Your comprehension does lack, somewhat. Try again.