No, Decimation (Latin: decimatio; decem = “ten”) was a form of military discipline used by senior commanders in the Roman Army to punish units or large groups guilty of capital offences, such as mutiny or desertion. The word decimation is derived from Latin meaning “removal of a tenth”.
However in digital signal processing, you are correct. When the term decimation is used in DSP is does not specifcally require a factor of ten, as you can decimate by 2 or any other number. But if you decimate by 10 you delete 9 out of 10 samples, reducing the sample rate by a factor of 10.
Regardless, the youts are using it incorrectly based on the original definition.
The ‘youts’....I know what Joe Pesci movie you have been watching!