A produced accepted kWh is absolutely equivalent in terms of emissions reduction. It is one to one, over an annual timeframe. One renewable kWh in, one fossil out. This is a record of power actually supplied, not instantaneous capacity or whatever. KW is instantaneous, provided kWh is historical.
I think you’re just making different points about economic value or grid reliability. You’re probably right about those things! You are concerned about the grid integration and reliability of solar, which is fair. And those issues may impact the ability of solar to get higher grid kWh contributions than today.
but these points don’t take away from the facts in the article - that solar produced and this displaced more emissions than nuclear in the last year.