Photographers of the Edwardian era would have been perfectly able to alter photographs.(Not sure what reason there would be for photo-shopping anyway? A lot of Titanic/Olympic construction photos were doctored in various ways, but I don't think they had they technology in 1912 to implant people or transpose heads onto bodies).
An experienced, professional photographer of the time would have found it quite easy to manipulate. In fact "spirit photographers" had been conning money out of people since the 1860s by putting ghostly people (actors, assistants or paper cut outs) in full form or just their heads or hands into a photograph of someone sitting for a portrait.
For a few years after WW1, many photographers in Europe, North America and Australasia offered a service to people who had lost their lost their son, husband or brother in the war and wanted one last picture with them. The relatives would go to a photographer with a good clear photo of their relatives head. They would have their picture taken with a ringer taking the place of their relative. The photographer afterwards would cut out the ringers head and inserted that of the young man they wanted one final picture with.
My local photographer taught me all that. You need to have something to talk about when the football season's over.