Ah well, I only wish I'd had the guts to tell that to my aforementioned professor. This guy was out for blood, and that was only one of the nitpicky things which he kept commenting on. Plus it is possible - I'll look through a few papers and see - that in scientific journals the data-plural thing is still consistently used, although in popular speech it is not as common. There are plenty of other grammatical constructions in our papers which seem like garbage to anyone else reading them, but are the most efficient or most clear way to express a thought!