Just a quick reminder that Manton’s of Calcutta called the 7mm 140 gr load, the “.275 RIGBY, No. 2 H.V.” in their 1925 catalogue (page 104). ...so regardless of Corbett's characteristic 'British' under-statement, the ".275 Rigby" name has been legitimate in India at least for just shy of a hundred years.

Not sure what is to be gained by insisting this is not so.

To be clear, only the 140gr High Velocity cartridge was so-named, the 172gr standard velocity cartridge being referred to as the .275 Mauser. Discussion on page 80 of that Manton catalogue cautions against confusing the two .275s, but only for reasons of ballistics and sight regulation. No throating issues are ever mentioned.