As the old joke has it: a million here, a million there, and pretty soon you're talking about real money!
But on the important subject of units and symbols for units, when you were a working chemist @henddraig, had the SI system not come in? Perhaps it didn't affect chemists to the same extent as physicists and engineers.
When I was at secondary school, in the lower school we used the so-called CGS system - centimeter-gramme-second system, but by the time I was doing physics in the 6th form, we had moved on to the MKS system - metre-kilogramme-second. I'm not 100% sure how the process worked, but what became used in the SI (Système international) were the MKS, rather than the CGS units.
I guess you are referring there to the adoption of SI units, but as you also suggest, in practice people probably carried on using what they had been used to, for a long time, anyway.