As an example of motherboard manufacturers going outside specifications, my MSI motherboard has a built-in option to change BCLK, which is the clock reference for the entire PCIe bus. Changing it not only overclocks the CPU, but also the GPU's connection (not the GPU itself), as well as the NVMe SSD.
This was so not-endorsed by Intel that they quickly pushed microcode that shuts the CPU down if it detects BCLK tampering.
In response, MSI added a dropdown that allows you to downgrade the microcode of the CPU.
So yeah. Very not within specifications.
If I run the chip in a way not documented by the manufacturer, or modify the ECU to allow the turbo to generate more boost, those are both unsupported modifications, and I'd consider either of those "overclocking"
This "I can run a core at a faster speed" is a documented feature so not really overclocking.