It is worth bearing in mind that it can be seen as stored energy that can be used at any point in time, unlike wind and solar.

In other words, 5% as an average means it's far higher during periods lacking light and wind.

Solar is down as 4.4%, though in peak Summer during the day it can satisfy about a 1/4 of demand, cheaply.

It’s not clear if solar includes reduced demand from rooftop solar, or just grid connected solar

Either way 5% is a tiny amount.

biomass is also far better than gas for those times when you do need to boost supply, so increasing biomass still seems like a win.

agreed. It can seem counter-intuitive with biomass since it's "burning trees", but generally it's a carbon neutral process or far closer to one than burning buried fossil fuels.