Amber Electric in Australia has this same model of passing the wholesale prices on to customers.
But they have a cap.
"We pass through the 30 minute wholesale prices directly, and this is typically significantly cheaper than the Government’s Default Market Offer, but to give you peace of mind we guarantee you will never pay more than the Default Market Offer (or VMO in VIC) over a year or we’ll refund the difference."
https://help.amberelectric.com.au/hc/en-us/articles/36003745...
I think this is only possible because there is lots of regulation on electricity providers in Australia.
I think this is only possible because there is lots of regulation on electricity providers in Australia.