I'm not aware of this being a requirement. It's true only if the system being installed is underpowered to save money on the system cost. The special high-efficiency refrigerators and related high-efficiency appliances are needed then. If the system is sized for the load then no special accommodation is needed. I've known people with electric stove tops & convection ovens, hot tubs, and large HVAC systems that run off their large off-grid power systems just fine. It's all in how much someone is willing to pay for the system. Systems that give a normal grid-connected experience can be very expensive but still be less expensive than running a power line in.Remember too that off grid will typically entail specialized expensive appliances that often are excluded from the "system" cost.
It's when homeowners get a utility estimate of $150k for the power line and think they can put in an off-grid system for $10k that operation expectations are not met.