The initial implementation of the new switch did not work with the 'latest' release of evcc https://github.com/evcc-io/evcc/releases/tag/0.132.0 cause of a tiny bug in evcc that will be fixed with the PR evcc-io/evcc#17951.
But instead of waiting for the next evcc release (which will be available for sure quite soon), I have implemented a simple workaround (using 0 & 1 instead of true & false at the API endpoint).
All the best for the new year!