Solar panels receiving indirect sunlight Indirect sunlight produce around 10% to 25% of their optimal output. A solar panel of the size illustrated could optimally churn out around 4W with direct sunlight or 0.4W with indirect sunlight.
The website for that light suggests it has a nominal wattage of 3W.
So. If you had 12 hours of direct sunlight, you would easily get 12 hours of full luminance LED light. It might even get 16 hours of full luminance if the battery is up to it.
But if you are only getting 10% power because of the indirect sunlight, then you'll only get a tenth of that, so 1.6 hours of full luminance. If it runs at 20% luminance then you'll only get 1.6 / 20% hours, which is still a good eight hours.
But I've ignored the battery, the various other power draws and efficiencies.
That seven hours minimum charge time with indirect sunlight isn't going to give you 12 hours of 20% lighting. Its going to give you about five hours, maybe four hours.
In answer to the headline question:- Yes, light fixtures with small solar panels require direct sunlight. They'll still work a bit with indirect sunlight, but they won't do everything you expect of them.