I can fully understand "bickering" about someone sprinkling their favourite data type over a codebase which consistently used a standard data type before. The argument that it might be multithreaded in the futurure does not hold if the rest of the code base clearly was not writen with that in mind. That could even be counter productive, should someone get the misguided idea that it was ready for it.

Make a (very) good argument, and suggest a realtistic path to change the whole codebase, but don't create inconsistency just because it is "better". It is not.