While "where tradition meets innovation" is a set of words that the county puts on their logo, and appears to meet the definition of a motto, the parent is correct that the Official Motto is indeed "I Byde My Time".

https://www.loudoun.gov/177/Coat-of-Arms

"Where Tradition Meets Innovation" appears to be a branding push by the county dating to 2019 rather than an official motto. https://www.loudoun.gov/ArchiveCenter/ViewFile/Item/8563