GG has inadvertently stumbled onto something but for the wrong reason.
Inverter:- An electrical/electronic device for converting AC into DC. The DC is easier/used to allow for modulation of the compressor speed. A smaller capacity air condioner unit cannot modulate down if it is running at maximum heat load.
So if the compressor is going to be modulated down at normal heat load it needs to run at, maybe 70%. So yes an inverter equipped system needs to be larger than a conventional on/off unit. A side benefit from this is that when running at 100% a larger unit will initially cool the space faster.
So for say a small bedroom 12,000 BTU rather than a conventional 9,000 BTU.