The R class was not designed as second-line battleships

Were the R-class battleships intended from construction to be obsolete second-line ships?

No; they were conventional battleships built to increase numbers economically, with fuel-supply concerns shaping their design.

The Royal Navy did not deliberately build the Revenge class as second-line battleships. The Queen Elizabeth class was the qualitative program, while the R class followed a more conventional design intended to increase numbers. Their design choices reflected cost and concern about dependable oil supplies rather than an intention to accept obsolescence. The attempt to obtain more ships for the available money did not make them disguised second-class capital ships.