People who vote green know they won’t win an election, but do so anyway to pressure the larger parties to do more about climate change. The Greens themselves achnowledge this.
However, the pressure won’t have much effect until they start actually taking seats from them. Standing down to give Labour a clear shot would destroy their steady gain in momentum and spoil the best chance they’ve ever had to get more seats.
I agree, which is why I’m voting Labour in a Conservative stronghold. Granted they would still be the largest party after losing those 4 seats, even if they don’t reach majority they’d still be able to make a coalition, most likely with the Lib Dems.
That claim by Labour probably has about 10 caveats that would further delay proper decarbonisation.
We also need to decarbonizing everything, not just the grid. Get people out of cars and onto bikes/transit, switch vehicles to renewables, reduce plastic use and meat consumption etc. Pledges for these would require action that would antagonize the majority of Labours voter base so they’ll never make any of substance.