Why do people say Rajputs came after 10th Century when The Buddha uses the term to refer Kshatriyas?

Many folks say the term Rajput is not synonymous with Kshatriyas but The Buddha clearly mentions it in Sutta Nipata (pg. 106) [ Source: https://ignca.gov.in/Asi_data/892.pdf ] and uses it to refer Kshatriyas.

.

So isn’t anyone claiming Kshatriya status claiming to be Rajput as well?

DISCLAIMER: THIS IS NOT MEANT TO BE A CASTEIST OR RELIGIOUS QUESTION. THIS IS JUST TO DISCUSS ABOUT THE ORIGIN OF RAJPUTS. PLEASE DO NOT ERRONEOUSLY MISINTERPRET THE QUESTION.