In general that's correct.

Though with some FTP servers (like IIS) that do not provide the timestamp in UTC/GMT, some additional configuration might be needed to achieve this.

Is the file timestamp driven by the site FTP settings? The attached file contains an example. I'm in ET, and assume this indicates the files were sent 8:31am ET. Someone in PT should still see 8:30am ET timestamp, versus 5:30a PT, correct?