The word "guaranteed" is about lowest variance - most predictable. What is prone to unscheduled maintenance, breakdowns, forced outages, etc.
The forced outage rate of solar is almost 0, wind is about 1%. https://rmi.org/fuel-hand-make-coal-nuclear-power-plants-val...
In practice, forced nuclear outage is 1-2%. An additional 7% downtime is scheduled outages for refueling. Coal is about 15%.
Here's a live report: https://www.nrc.gov/reading-rm/doc-collections/event-status/... You can see about 7 are offline.
Disruptions are normal, daily, common occurrences and in practice, solar is pretty reliable in places like the Southern California desert where the grid-scale installations are built (example: https://www.google.com/maps/@34.7923792,-118.4060493,17707m/...). They are subject to occasional monsoons, but that's why there's more in other places such as down near the mexican border (https://www.google.com/maps/@32.7188416,-115.6454361,19457m/...).
This is still early, scroll down to the map here: https://www.seia.org/research-resources/major-solar-projects... ... that's the kind of redundancy we're talking about.
You can wonder why all you want but hobbling together headlines some of which are 3 years apart and pretending they're related is the thing you actually should be wondering about.
By the way, my source of information is mainstream French media.
Except it doesn't. Which is why Germany didn't decrease its gas plant capacity. They're needed when there's no wind.
> The forced outage rate of solar is almost 0, wind is about 1%.
The issue with wind/solar isn't forced outage. It's that the wind doesn't blow all the time, so comparing how much cost 1MWh of wind when the wind blows with 1MWh of coal is dishonest. You're comparing apple and oranges.