IIRC, those started out as DIY field adaptations. Necessity is the mother of invention.
You're right . It was only after D day when the Allies got into the bocage country and tanks were getting hit in their " soft underbelly" that the Rhinos got built.
They covered arc welders and Shermans with tents so they could work `round the clock and welded steel `teeth’ to the fronts of the Shermans so the tanks could cut through the hedgerows.
The Germans had our guys channeled into fields of fire. (Something like San Jose police and Trump rally participants.)