Yeah, single channel tends to really hurt the performance of integrated graphics in general, as can memory speeds, to a lesser extent. The difference between DDR4-2400 and 3000 can affect performance of the integrated graphics by around 15% or so. Going from dual-channel to single channel can cut performance by about another 40% though. So, between the two, you might be looking at around half the graphics performance of the same processor tested on a system with two sticks of higher speed memory.
And really, it's likely not worth saving a few bucks on memory just to halve your graphics performance. A 2 x 4GB kit of DDR4-2400 costs around the same price, or maybe about $5 more than a single 8GB stick of the same speed. Or for about...