Based on the available information, Clay does offer some function-specific headcount data through the People Data Labs integration, which includes "Employee Growth Rate 1 2 Month By Role" as an output field.
The main "Find Company Headcount Growth" action appears to primarily track overall company headcount growth over time using LinkedIn data, without specifically breaking it down by function.
If you need more detailed function-specific headcount growth analysis, you might want to explore the People Data Labs integration further, as it seems to offer more granular data about employee growth by role.