There is no carbon neutral fuel before we have a surplus of carbon neutral energy. Currently, any kWh you use to synthesize fuel could instead be used for something else. It's probably less carbon intensive to keep on burning regular fuel, because it takes a lot of energy to make synfuel.

Of course it's nice that they subsidize R&D for synfuels (we might need them for niche applications after all), but selling them as "carbon neutral" is just greenwashing.

They have been thinking about it. You haven't:

https://arstechnica.com/cars/2021/09/porsches-new-synthetic-...

https://www.siemens-energy.com/global/en/news/magazine/2021/...

How do your links counter my argument that any kWh spent on creating synfuel could be used for something else instead and as long as we don't have a surplus of carbon free energy all the carbon free electricity used in this way needs to be compensated by fossil fuels somewhere else in the grid?

I don't think this argument makes any sense. Just because there can be better uses for additional clean energy, does not make the additional energy any less clean.

By this definition, no source is clean, because there are always "better uses" for energy.

The honest way is using the average CO2/kWh for the grid you're plugged into (including the CO2 emitted for constructing the power plants with some discounting function) to estimate how much carbon your synfuel releases.