I would not agree with that. I am pretty certain that total surface area is all you really have to care about when it comes to comaring real images rather than individual pictures. I've put together some posts with pictures to illustrate my point. Maybe you can have a look and point out to me what you consider wrong and why: https://www.canonrumors.com/forum/threads/equivalency-now-with-pictures.39787/post-874838I honestly think that both of those are kinda "wrong" -wrong in quotes cause it's not the crop that's effecting either, it's what you do to create an equivalent full frame image.
Light gathering is done on a per pixel basis, not on total surface area. If there are any exposure differences it's due to equivalence issues or pixel size and the way that the signals that those pixels produce are being amplified. Smaller pixels are less light sensitive than larger ones.